If you fail your bac and need to repeat your terminale you may want to do this in a different lycée. But, be warned, it is difficult to change lycées (unless you have moved house) at any time and extremely difficult to do so when you are redoubling terminale.
Indeed, you are lucky if your current lycée agrees to take you back to retake your bac as it is not obliged to do so once you have reached 16.
In addition, you may get permission to move lycée but end up in a "dump" school the other side of the departément.
So, think carefully before applying to change lycée after a failed bac.
The process of changing lycée at the end of seconde or première is not straightforward either - unless, again, you have moved out of the area or you want to switch to a course that is not offered in your current lycée. But even this latter reason is frowned upon so better to think ahead and make sure you choose the right lycée for you when you leave collège.
Even so, there are many reasons why you might want to change school: bullying, because you don't want to redouble in the same school, being picked on by a teacher, because the standard is not what you expected.
If you really do want to change, be prepared to argue your case convincingly
To request a change of lycée, you need to contact the proviseur (head) of your current lycée who will fill out a dossier to send to the lycée you want to move to. This dossier will then be sent on to the inspection academique who will rule on the request.
Ideally, meet your proviseur in person to discuss your request and to convince him or her of your reasons for wanting to move as their opinion will be sought on the matter. So it is better not to go on about the negative aspects of the school you want to leave - rubbish teachers, rubbish school, truancy levels etc.
If you do not want to go through the proviseur, you can compile your own dossier, which should contain copies of your school reports, proof of address and a letter explaining why you want to change schools, and send it direct to: la Direction des services départementaux de l’Éducation nationale (google this with the name of your departément to find the address).
You will also need to make contact with the head of the lycée you want to move to. Ideally, arrange to meet him/her – if they know or have met you they are more likely to support your request.
Again, try to give them positive, concrete reasons for wanting to move rather than just complaining about your existing school. Where possible, back up your arguments with evidence - e.g. doctor's confirmation of bullying or unanswered complaints to the school etc.)
Finally, to give your request the best possible chance of success, start early in the year - ideally by January - as the proviseurs are increasingly busy towards the end of the school year.
Obviously, in the case of redoubling terminale after a failed bac, this is not possible so you need to act as fast as possible.