What do you do when you have students who clearly already understand the material you are about to cover in your next unit? You can allow them to compact out of the unit. While students are "compacting," they are mostly independently learning about the topic at hand, giving them the opportunity to extend and deepen what they already know. In my classroom, I gave this opportunity to students who score in the top 3% on a unit pretest, and those students who chose to participate also had to have parental approval and support.
This resource provides a task list for students participating in this independent study as well as a daily check-in sheet that teachers can use as a daily accountability assessment.