Our middle and high schools have differing schedules due to multiple staggered lunch periods. Since the current set up assumes that the start of the next period is the end of the previous one, teachers are having to create their own ad hoc schedules.

For example, 4th period for 7th grade starts at 11:30. 8th grade though has lunch during 3rd period so for them 4th period doesn't start until 12:10. As a result, when they select from the pre-made bell schedules their 3rd period ends a half hour early because the next period in the schedule starts at 11:30.