ASM shows old classes under the teacher. Can I delete them?

We sync from IC to ASM to Jamf. In ASM it lists 65 classes this teacher is connected to but he is only teaching 6 classes. The other classes are from previous years that he is not teaching this year. Are classes in ASM "archived"? Can I delete them if not active this year? How do I get ASM to only look at classes active this year to sync in? If I delete old classes in ASM will they resync?