Simply replace the unfilled areas such as "" and "[date]" with your information.
Dear [name of teacher],
I would like to thank you for taking the time to meet with me about [name of child]. I am very appreciative of the time, effort, and attention you have devoted to my child, and felt that our meeting was very productive.
I look forward to working with you throughout the rest of the year to insure that [name of child] is doing everything [he/she] needs to in order to best meet educational goals. If you need me to assist you in anyway, please let me know.
Thank you, as always, for keeping me informed. I really appreciate the extra lengths you go to in this area.