Student Exchange Programs

I will be going to France August 26th for a year long exchange. The program has told me i must stay for 11-12 months, however my visa is only for 11! Students to other countries all have 12 month visa’s and mine is for 11. I would like to stay for the 12 months, especially because there is a huge festival in my future city at the end of July that i don’t want to miss. I will turn 18 this december, and i was wondering if there is any way i can extend my visa for 1 month?