I don't know of any encyclopedia which would be allowed for written education-related works in school because the goal is that students should learn how to research properly, however for presentation work it wholly depends on your teacher to which degree it's permitted for use and usually it's required to limit it to the external sources used within that article. For study-related works it's however not allowed mostly because the scope and level of information as well as language and terminology used in encyclopedias is generally not compatible with scientific standards mainly because you could post information without understanding and without verified accuracy of that information.
However I do see Wikipedia as an open-source encyclopedia in general and writers tend to have a lot of biases, may it be in political, scientific or philosophical terms but it is not a medium that is restricted to one nationality and pretty much open to anyone. It also doesn't shy away from criticism which is important for future development of the medium.