Oh, gross! Oops, sorry; I just pictured myself having to do that and NEVER!!!
I am not an elementary school teacher, so you’re best to ask one. However, the behaviour still sounds like typical behaviour of my high school students and I will try my best. Usually, I have to do things in increments, like no more than 15 minutes on one specific thing. Make it connected to the students and interactive; get the students out of their seats, whether it’s in front of the class trying something new or working with a partner/small group to discover something. Eventually, bring them back around to share what they’ve been doing. Again, I’m not sure of the logistics in a grade 3 class, but try to keep things different and fun for them!
Teaching In Real Life 