I'm simulating some tests, and I need educational texts to design my tests according to. So if anybody knows any webpage, social group, or even book, that can help me provide these texts, please let me know.
You can start by exploring the ERIC database - http://eric.ed.gov/ - you can search and download full-text articles, as well as the Linguist List publications database- http://linguistlist.org/pubs/papers/index.cfm. Here is a link to their writing resources page - http://linguistlist.org/studentportal/writingresources.cfm
and Ask a Linguist feature http://linguistlist.org/ask-ling/ where you can search for questions or submit your own query.
There are many other open access sources, e.g. see UNESCO Open Access Portal http://www.unesco.org/new/en/communication-and-information/portals-and-platforms/goap/thematic-areas/