Several years ago our stake reversed the order of meetings. We now start with RS/PH, then Sunday School, and last is Sacrament Meeting. No class goes overtime when Sacrament meeting is the finale; it just doesn’t happen, it is too obvious that a teacher isn’t letting class out in a timely manner if the class members straggle into Sacrament meeting.
At first people were getting to RS/PH/Primary/YM/YW a little late, but when the leaders started on time, folks started getting the idea that their children would miss their assignments, and announcements would be made whether they were there or not. A miracle occurred as after a few months, people were getting there on time.