LOL - Okay, I know you didn't post this for humour but you have to admit, it it kinda funny - when it's happening in the past or to someone else
Seriously, I caught Ginger on our table once, just up there walking around. Mr Fun Kitty doesn't even do that! Well, fortunately, she must not have found anything good, cuz she's never been there again.
I honestly don't know what I'd do. When Fun Kitty was determined to get on our mantle I lined it with coke cans full of pennies. Came home one day to some coke cans on the floor, and he's never been up there again.
The problem with that for a dog though, is dogs are just so much more clumsy than cats. Even being startled, I'm sure the cat didn't hurt himself. If your guy's anything like my girl, she'd startle and end up hurting herself getting off the table. So I wouldn't want to recommend that.
Yikes, other than keeping the chairs tucked (much easier said than done, i know), I have nothing.
Well, good luck!!!! Sorry about your little ones homework!