For Most Classrooms:
Direct Connection to iPad via Cable (lightning to USB cable). This allows you to present your iPad screen to any supported macOS computer. The computer screen can then be displayed on the classroom projector.
For Apple TV Equipped Classrooms (APEX, Mead Elementary, and Erie Highlands):
Classrooms equipped with Apple TVs can support wireless projecting from an iPad or macOS computer. Here is an article that outlines the best practices for doing so.