Simply replace the unfilled areas such as "[]" and "[date]" with your information.
Dear [name],
We were extremely upset to find out that [name of person] was placed on [probation, suspension, expulsion] , though we understand the reasons for this action.
We do not condone misbehavior of any kind and we understand that [name of person] must be reprimanded. We are thus prepared to cooperate with the school to insure that [name of person] becomes responsible for his behavior. We have discussed this matter with [him/her] already, and [he/she] is aware of this matter.
We ask that you please accept our apology for the problems that [name of person] has caused for you and the other teachers. We know that everybody is going to see a huge improvement in [name of person]'s behavior.
Sincerely,