Students may learn the grammatical points at hand in a very short time, but the integration of those grammatical points into their inter-language, gaining the ability to actually USE them whenever necessary takes much more time.
So, when you do some accuracy based exercises, there seems to be no problem but as soon so you move on to some less controlled fluency based exercises things get a little ugly. So what then?
1. move on and teach the next grammatical points, hoping that they’ll put it all together over time
2. Don’t cross the red line! No more points until they’ve mastered the previous one first.
If you go for option one:
You might end up having students that know what a passive sentence is, but as they open their mouths they make mistakes as in “he read a book” or “what is he want?”
If you go for option two:
How much practice and time do students need to get to that point where they can USE them? Where do you find that vast amount of exercise they need in order to roughly master the point at hand?
What do you think?