Document every incident. Keep a written log with times, dates, and NAMES. Use neutral language, and document as "DD reported today that...," but do not downplay the action, if a touch was unwanted, don't say "he hugged her," but "he hugged her against her wishes." Keep this document. Until you are ready to disclose the identity of the perpetrator, send a redacted copy of your entire log after each incident to the school councilor, simply adding each new report above the log of the previous.
This would seem to be particularly helpful in gaslighting situations.
