Dear …
I want to thank you for allowing me to work along side of you in your classroom this past year. It was a real pleasure to work with you and it provided me with a great opportunity to __(briefly describe what this did for you)__. You have a tremendous amount of patience and compassion for your students and I can certainly see why you are able to build such a great rapport with them.
It was a privilege for me to work with a person with such passion who upholds real professional etiquette in the classroom. Your expertise definitely shines through as you deliver your course material. You do a commendable job with your students, __(Name)__. It was both an enjoyable and informative experience for me.
Once again, thank you for welcoming me as a member of your classroom this past year. You are a credit to the teaching profession.
Sincerely,