How to manage younger sibling at home while older one is "working"? [View all]

Our 1st grader is at home this year and his younger brother can "sniff out" when we are "doing school" in about 4 seconds. He pouts, yells, throws tantrums (and toys). I can engage him in the activity for about 5 minutes and then he wants his brother to play.

My saving grace is that he goes to 4K for 3 hours almost every day and then we get one on one time. Any thoughts how to incorporate him into the projects?