"Thank you so much for everything!"
"Jake has made so much progress with you, we can't thank you enough, it has made such a difference in our lives.
And thank you for working with us as well as Jake to show us how to help Jake and understand Jake.
Your work makes such a difference! We will miss you so much, all the best for the future."
(The name has been changed to maintain confidentiality, and permission was granted to share this.)