Are you getting ready for the fall? What grade(s) and subject matter will you be teaching? Being a science teacher at heart, I would like to say that you will have no trouble keeping your students engaged the whole period with engaging, rigorous lessons. But we ALL know that is only part of the recipe for success in classroom management. There are numerous articles in the NSTA Learning Center that address this. See below.
Knowing each of your students - their strengths (and support needs), their passions and hobbies, their physical and emotional needs, etc., will help you to individualize strategies for specific students. There might be ways the students who finish early can use their time to prep for the next day, or there may be activities in place that they can delve into that will provide additional reinforcement or enrichment from the lesson just completed. Perhaps some students can become peer tutors/mentors and provide support and encouragement to those needing additional help. Or if it is toward the end of your unit, consider having a way to allow students to gather information and summarize a unit with this idea from the January 2020 Science Scope:
Kids teaching kids: https://common.nsta.org/resource/default?id=10.2505%2f4%2fss20_043_05_20
I am looking forward to hearing about your upcoming school year, Jacqueline.
With kind regards,