Use one of the Arduino Uno kits and follow the projects in the Arduino Projects book. Some projects are short and can be completed in under 30 minutes. The later projects may require a few class periods to complete. All projects can be expanded and customized to go beyond what is in the Arduino Projects book. The book has 15 different projects. Mr. Didier recommends doing at least the first six projects in order if you have limited experience with small electronics building or work with an Arduino. The later projects can be done in any order, but they do loosely build on each other in the book.
Below is a rough roadmap for class projects with beginner Arduino projects. Coding can be done on the MacBooks in class or using the online Arduino code editor. You do need to make an account and password with the online editor to save your work online.