You can record and agree with him to take your patent application in parallel, settle the matter through consultation so that you can enjoy the right of signature, or go to the patent office to change the name of the design inventor or abolish the patent.
You can also use recorded evidence to suggest to the school that the teacher has infringed your intellectual property rights if negotiation fails. Let the school impose administrative penalties on it, or let the school advocate increasing the number of designers after reporting. If it is really in the name of the school, as you have always said, then the school can do so.
If it is an individual application, your recording and your original design concept will be quite proved, but only if your recording fully proves what patent it is. You can file a lawsuit