There are two types of accommodation, one is a school dorm room; the other is rent an apartment. School dorm room can cost from 150€ to 300€. An apartment including bathroom can go from 450€ to 750€, accommodation in suburbs can cost from 200€ to 350€. One interesting thing is that the French government gives an amount of 100€ to 200€ to students in order to help them get accommodation, this help is depending on your financial situation.
Affordable accommodation in Paris is hard to find and flat hunting is a real challenge for all newcomers. The websites below may be of assistance:
http://etudiant.aujourdhui.fr/etudiant/info/logement-etudiant.html (search tips - in French)
http://www.seloger.com/etudiant.htm (student residence search engine)
http://www.immojeune.com/ (student accommodation search engine)