As an assistant, you are entitled to a Pass Éducation. It’s one of those things it would be nice for you to be informed about at orientation, but you’re not. It’s a pass that allows you free access to all National French museums and monuments. Granted, yes, your visa will often do the same for you if you’re under 25, but this card is a lot more convenient.
How do you get one? Simple. You go ask the secretary at your school and they should have some on hand. Have a passport-sized photo on you because the secretary will attach it. It’s supposed to be a French sized one, but if your photo isn’t French sized, it’s not a big deal so long as it can be cut to fit without defiguring your face. If you need a photo, you can find photo booths that print official photos in most train stations and often at big grocery stores. Your secretary will stamp the pass to make it official, though I know an assistant who did not get her’s stamped and she hasn’t had a problem.
Where can you go for free with this card? Check out the list here. It’s conveniently divided by Académie.