You are already your teacher, you can say this directly to the teacher. First of all, you must politely ask the teacher if he has time, and then see if his daily life is convenient or if he is willing to take pictures like this. Maybe some teachers don't like to take pictures like this, and some old teachers like to take pictures like this. You can ask first, and then determine whether the teacher can take part in graduation photo's shooting.

But in the process of communication, you must be polite, and don't have any opinions on the teacher even if you fail. Then you can ask the teacher to bless you for graduation in other ways, such as giving you a book written by the teacher himself or signing your book.

Don't think so much, please ask the teacher first.