In France, all students have to join a compulsory state health scheme. Your healthcare costs will then be reimbursed 70% by the state scheme (Sécurité sociale) and 30% by a complementary insurance (mutuelle), which you have take out yourself, choosing from a range on offer. The two together mean that 100% of your healthcare costs are covered.
If you are a European Union national, you will need to apply for a European Health Insurance Card (EHIC) before you leave: this entitles you to French state health cover (Sécurité sociale), so you will not have to apply to join.
You will need to join the French state scheme (Securité sociale). You can do this online.
Apply to join
You can opt to take out insurance in your home country to cover your healthcare costs in France or you can sign up to a student mutuelle.
The student mutuelle (La Mutuelle des étudiants)