Simply replace the unfilled areas such as "" and "[date]" with your information.
Dear [name of teacher],
As you may already know, [name of child] has [name of medical conditions], which requires some special considerations. The school nurse is aware of this condition and is familiar with all the special requirements of the condition. [name of child] is also familiar with [his/her] condition, and is very able to communicate many needs that [he/she] may have.
However, it can be a source of concern or worry for those not used to dealing with these issues. If you ever have any questions or concerns, I would like to urge to you contact me. I would be happy to answer any questions you may have regarding the condition or [name of child].