Yesterday I coached two seven-year-olds, feeding them multiball for half an hour as they took turns practicing and doing ball pickup. Coaching seven-year-olds is like trying to catch smoke in your hands. If you haven't tried coaching this age group, then you have no idea what it's like. I've worked regularly with these two, who aren't exactly beginners. Both will likely become very good players. I should be taking videos of them now to blackmail them to show them someday.
I teach a class of beginning kids twice a week. Our last one on Sunday had 15 kids, including one 6-year-old, three 7-year-olds, and four 8-year-olds. So I'm quite experienced at threatening to throttle them if they don't pay attention teaching them the finer points of the game. It's always a matter of finding the balance between strictness (i.e. getting them to learn by actually practicing) and fun.
At this age they have an attention span of about three seconds. Okay, they can focus longer than that, but it's not easy for them. It is easier for a camel to go through the eye of a needle than for a 7-year-old to play serious for more than 30 seconds. Pretty much anything brings on a gigglefest. And yet you have to find a way to get them to do things properly, and to practice it, or as you explain to them they'll grow up flipping burgers at McDonalds they won't reach their potential as table tennis players.