"Bell-to-bell instruction" this was one of the mottos of Rialto Unified School District, my former employer. Even here in Thailand, that motto of "bell-to-bell instruction" rings in my mind.
End of the period, I've found, is a great time to turn one of the students into the teacher. They love it! One student comes up to the front of the classroom, and lead the students in a review of that day's Dolch sight words.