Here are some quotes about thanking teachers that I found:

- "A teacher affects eternity; he can never tell where his influence stops." —Henry Brooks Adams
- "The duties of a teacher are neither few nor small, but they elevate the mind and give energy to the character." —Dorothea Dix
- "The great teacher is not the man who supplies the most facts, but the one in whose presence we become different people." —Ralph Waldo Emerson
- "The mediocre teacher tells. The good teacher explains. The superior teacher demonstrates. The great teacher inspires." —William Arthur Ward

I hope these quotes help you express your gratitude towards your teacher. Let me know if you need anything else.