Negotiators for the Wissahickon School Board and teachers’ union have reached a tentative contract agreement. School Board Vice President Marjorie Brown reported the agreement at Monday night’s meeting.  She said it’s a three-year deal, but the terms will not be made public until both sides ratify it.  Union members took a ratification vote Monday, but the results had not been tallied as of meeting time and will not be released until the board votes on it next month.  The old contract expired on June 30.