The word material is used here meaning:
the things that are used for making or doing something (LDOCE)
In this sense, dictionaries list it both as uncountable => material and countable, plural => materials. So, all three examples are grammatically correct.
ODO Advanced Learner's dictionary gives examples that are closest to your intended use:
[countable, usually plural, uncountable] things that are needed in order to do a particular activity
As for the choice between "study", "teaching" and "education" per definition you should decide what is the purpose of the material, i.e. what activity would be performed using it - the name of the activity should precede either material or materials (whichever you chose).
From your example it is clear that this material is for students, not teachers. So, even though it might be argued that one student is teaching the other using this material, or that the material servers an educational purpose, the end goal of posting the material is for students to use it for studying. I agree with Ahmed on this; study material(s) would be my choice as well.