Simply replace the unfilled areas such as "" and "[date]" with your information.
Dear [name of guidance counselor],
I appreciate the time you took to speak with [name of child] about [issue]. It really has seemed to help, and it is always nice to know that the educators and employees within the school system are interested in each and every child.
[name of child] has always spoken highly of [his/her] interaction with you, and I am grateful that [name of child] has such a caring and dedicated counselor on staff at [his/her] school.
Thank you again. Please let me know if there is anything I can be of assistance with in the future.