I agree with Cheryl that Clips is a super intuitive video app, and the stickers and posters would be fun tools to help your students create an engaging commercial about your school.
If you're also looking to record audio separately through Garageband, here are a couple of great posts about podcasting for your school community:
School Podcasting - Reaching the Community
Best of luck as you bring this project to life!
Posted on April 06, 2023
Sounds like an engaging and fun project. Clips also has great features for making commercials. Clips “clips” can be added to iMovie for some fun text and animation.