You may now assign device labels to devices by uploading .csv file 

Device > Device Management > (...) on top right corner > Assign Device Label by Upload

Application: Reassign device labels for new school terms. 

Suggested steps: 

1) Enroll all new devices

2) Prepare an excel with columns: SerialNumber, Labels (multiple labels are separated by semicolon ;)

3) Remove existing device labels by Device > Device Labels > Bulk Action > Check Labels to be Deleted > Confirm to Delete

4) Device > Device Management > (...) on top right corner > Assign Device Label by Upload > Upload