score:8
The most obvious choice is to use a Navigo weekly or monthly pass.
A Navigo weekly pass covering all 5 zones (the whole Ile-de-France region) is 22.80 and is valid Monday to Sunday.
A Navigo monthly pass is 75.20, so that would probably only be worth it if you stay more than 2 weeks and start before a Monday and end after a Sunday.
Add to that 5 euros for the Navigo DΓ©couverte smart card on which you will load either pass.
This will allow travel on all metro, RER, bus, trams and commuter trains in the region.
There is a student pass (Imagine R) but I believe it is only available on a yearly basis.