Head teacher, I haven't seen him for many years, and I want to talk to him.

Hello, teacher XXX! I am (what school, what class, my name). Long time no see, I miss you very much! I feel lucky when I recall the time I spent with you. Thank you for giving me knowledge and wisdom. Teacher, how have you been recently? I really hope that my classmates and I can get together with you if there is an opportunity. I wish you success in your work and good health!

You can say hello to the teacher first and introduce yourself by the way. After such a long time without contact, the teacher should not recognize who you are. After all, teachers have many students every year. In the order of 1, 2, 3, 4. 2. Talk to him about his life at school and ask him about school, changes and so on. 3. Talk to him about his recent situation and so on. 4. Say whatever you want.