The choice depends on the learning subject itself. With respect to numerical calculations, my first choice would be BASIC, but my best choice would be Fortran.

Fortran has a simple syntax, it has been around since the '60s and there's an ever increasing body of ready software bearing a varying degree of coding complexity.

I would recommend a programming language that one can pickup and see the programming progess fast. Python comes to my mind as there are several books for kids on the market: http://www.google.com/search?q=python+kids+book

For kids in primary school i would prefer a language that is designed for kids to learn some basic programming elements. On a conference last year i learned of one language based on JavaScript named Isla, so nothing more then a browser is needed to run the examples.

http://islalanguage.org/

For Kids in secondary school you could use "real" programming languages like Python , but here i also would prefer JavaScript because of the fact that everyone that has a computer also has a browser, so no installation required. And you can not do too much harm to you system with JavaScript then with languages like Python. (like removing files that may or may not be important)

For Learning JavaScript there are nice open(CreativeCommons) learning materials of the OpenTechSchool.org for a Weekend course for people that have no prior programming knowledge.

http://www.opentechschool.org/material.html#javascript

Check Alice: http://www.alice.org/

Thanks for your feedback! Indeed, BASIC was the first PL I learnt (together with some Logo), but I was older than all my kids, actually. I agree that having an immediate view of what you get after some change in the program is important. I checked Alice and it is somehow what I had in mind. Its visual approach to the representation of program components (as graphical objects in a virtual world) is interesting to show how program sentences produce some effect during the execution. Isla is also similar but less sophisticated, of course. The good point is that it provides a connection between writing "english-like" program text and visualization. And their use through a web browser is definitely interesting. Alice has a complete programming environment where you do not need to 'write' any program text; instead, dragging components that are dropped in a program area is the way to build the program. This is also a powerful and interesting feature, with connections with professional programming environments. Python is a good trade-off between simplicity and more classical programming, where you have to use variables, conditional expressions and the like in a more standard way. But the command line/textual interface could be less appropriate for the youngest kids. Somebody told me that Ruby was also originally aimed at getting young people in touch with programming, and I actually found this interesting web page, for instance: http://kidsruby.com/

IMHO, this question itself need one more parameter, what the kids want to be?

If I should answer, the first language on actually should learn is visual programming, like construct 2, or any simple gaming engine, because they should learn thinking in Visual Concept first, visually. Elementary students can start here.

After they are mature enough, lets say, junior high school to senior high school, you can teach a more sophisticated but still visual language like javascript + css + html (Codecademy? Unity 3D?). This path can be for anyone.

Another path, jump in to Java / C++, strictly with Java Programmer Attitude (Qt, Android, etc), but, IMHO, not C, because C actually open to very different concept of programming, other than Visual Object. This path should be learned only when the child do has aspiration of technical / engineering / mathematical thing, like IT, Agriculture, Accounting, etc. Artist type student should stay out. :P :).

One rule I should say, to make the programming class fun, the students should code or create solution / games on the platform they have and can brag around about it. :)

Only teach C, or even Assembly to very mature students, to deal with its abstractness.

Good point, Renan. Actually, using web design as a first approach to 'programming' is also interesting for secondary or high-school students, because they are in strong contact with the web everyday. And the possibility of building their own 'expression and social platforms' is also exciting for them.

In my opinion the best way to teach programming is to use some scripting language (e.g., Python, Perl, Lua, Ruby, etc.) that uses some external library that allows the easy generation of GUI applicatons. For example, Python + pygame or Ruby + shoes are ideal solutions.

Scratch MIT could be a good starting point. TED talk: http://www.ted.com/talks/mitch_resnick_let_s_teach_kids_to_code.html

In my opinion for the first approach in programming a mixture between programming and engineering will be the best approach using commercial platforms like Lego NXT that allow children mounting their constructions and bring him life using a visual programming language (based in LabView). Is the same approach like the earlier LOGO (moving the turtle remember?) programming but adding more interactivity.

We have done this in some workshops and take a good feedback from children

I was a network administrator for primary and secondary education and one programming interface stood out as a great tool for introducing kids of all ages to the concepts of programming. It is called Scratch. Here's a link to their website http://scratch.mit.edu/. Scratch contains a lot of templates to get kids started on their way to programming experience. The appropriate amount of help and intervention provided by the interface can be adjusted to suit the ability of the individual.

Indeed, I'm very grateful for all these pointers and suggestions. It will take some time to take a detailed look on them, but I'm sure they will be useful to motivate my kids to use computers not only to play and navigate but also to write their own games and web sites...

You can't go past Seymour Papert's Logo language and environment. http://www.papert.org/, http://en.wikipedia.org/wiki/Logo_(programming_language)

Logo was good for the 1970s or the 1980s but not for the 21rts century!

@Apostolos: Well, let's agree to disagree. People tend to think that just because something is old means it's obsolete, but it ain't necessarily so. I don't think the human brain has changed much in that time, and Logo was designed to make it easy for children to learn the basic principles of computation and to be able to play with them freely. Once they've got that, they can easily move on to other languages and environments. If you've spent more than about 5 minutes with "visual programming" in Scratch or App Inventor, it rapidly gets frustrating finding the right blocks and moving them around. Much easier just to type some simple commands. (And improve keyboard skills at the same time.)

Well, as I mentioned, Logo was one of the first languages I learnt, and, as a beginner, I found it interesting and exciting, mostly because it showed that the output of a program execution does not need to be a numeric computation or a register with information about people (think of the 80s). Actually, I would say that Alice, for instance, can be seen as a kind of 'successor' of Logo in that the outcome of the program execution is a virtual world (pictures and movement, rather than alphanumeric information).

the programming is very hard and i can't imaging the most of the children thinking in complex programming tecnologies, because it can cause that they rejects programming. For that in my opinion scracth is a very good options for children. Because they can learn the way as the program work and they can enjoy it because it is like a game and they get visible results with their programs.

Don't forget my previous post, for kids, not only giving them time to learn, but give them priviledge to brag on the product they made for their gadgets / mobile phone / anything they can bring anywhere. (which, sorry, Logo, Alice, and Codecademy fall short compared to real productivity tools like Construct 2 and GameSalad).

@Ian Barnes I completely disagree with you! LOGO is obsolete because it has nothing exciting to offer. Young students can easily draw squares, circles, and other geometrical shapes with many different tools. I have taught LOGO and I can assure you that people find nothing exciting about it. Nowadays, people use windows, panels, and buttons and people want to learn to make applications that produce GUIs. Just because something worked once, it does not mean it will work for ever!

Besides everything that has been mentioned earlier, think about letting them tinker with a set of Notorious Construction Block Danish Brand™ Mindstorms. They allow to build machines with sensors and actuators, programmed using a graphical, drag-and-drop very intuitive kind of language that is basically a simplified version of National Instruments' LabVIEW. Even though watching programs executed by a computer can be gratifying, seeing their effects in real life takes the gratification one step up - and with all the optical/acoustic/contact sensors, it's a pretty nice introduction to robotics as well.

Nice connection between programming and robotics! Actually, for those who love such construction toys (Lego and the like), this brings a new dimension to the use of programs 'in real life'... Thanks!

Try http://code.org

it very interactive and focused on school children and it teaches programing in a fun way

Scratch is a programming environment designed by MIT Media lab to lets kids make games, animated stories, interactive art, and share with others on the Net....It is just amazing....and above all it is interactive method of learning programming...

http://scratch.mit.edu/

You might want to try out Raspberry Pi. It's cheap, it comes with a full operational Debian Linux and it uses Python for programming language. Besides tutorials are already available online. You can also check out this article: http://www.techradar.com/news/computing/8-great-raspberry-pi-projects-created-by-kids-1143243

I recently discovered a survey paper by McNerney (Pers Ubiquit Comput (2004) 8: 326–337, DOI 10.1007/s00779-004-0295-6). It provides an historic account of educational computing research at MIT, focusing on physical interfaces. So, children really build (rather than just write) programs! Enjoy!

Another couple of links: http://bootstrapworld.org and http://wescheme.org . Bootstrap is a curriculum aimed at middle-school students, using the lure of video-game programming to motivate concepts like Cartesian coordinates, conditionals, data types, iteration, etc. WeScheme is a development environment in a browser, complete with a nice beginner-friendly graphics-and-animation library, to go along with the Bootstrap curriculum.

(I have no formal connection with Bootstrap or WeScheme, although I've taught a similar approach to college non-majors for years.)

Thanks Stephen! Indeed, this looks interesting. And having a complete internet-based interface (using a browser) is a very good point!

But programming is also fun! At least this is my own experience. And, of course, I'm not saying that kids should not play. Just think of programming as a kind of game...

I guess you are right when it comes to kids at primary education, but secondary education is something else!

If you have linux as your os and you are familiar with KDE you could try "kturtle" which is a programming language for kids. please visit :

http://edu.kde.org/kturtle/

One may also try Alice from cmu.edu.

If you want to teach programming language, firstly, you must teach algorithm to kids. I would recommend Microsoft KODU or MIT Scratch for a funny introduction to programming. Both of those programs are free...

You can visit here:

http://www.kodugamelab.com/

and here:

http://scratch.mit.edu/scratch_1.4/

Thanks Mehmet and Hassan for the pointers to "algorithms for kids", which is also interesting issue!

The Visual Basic programming environments are considered the most appropriate for  teaching programming basics and are often used for introductory level courses.  Visual Basic scripting language is an interpreted language, meaning it does not need to be separately compiled or linked.  A built-in interpreter reads the program and executes the statements from a simple text file.  This simplicity allows rapid development, testing and learning of the basic language constructs.  It also is a fairly rich language, and contains libraries for most major file and operating system operations and tasks.