When I was running primary school chess clubs I would occasionally go up to a student during the game and ask four questions.
1. What was your last move?
Quite often, they were unable to tell me, because they weren’t really concentrating on the game. First lesson: you have to concentrate at all times when you’re playing chess.
2. Why did you play that move?
They’d often shrug their shoulders and look bemused that I could even consider asking that question. Or if they gave a reason at all, it would be “Because it’s safe”. Second lesson: when you’re playing chess, every move must have a purpose and be part of a plan.
3. Why didn’t you play this move instead?
(I’d select a plausible move rather than a pointless move or an obvious blunder.) Again, they wouldn’t be able to answer that question at all, because they’d just play the first move that came to mind. The idea of considering alternatives and choosing the one you like best was totally foreign to them. Third lesson: you need to develop breadth of vision, to consider several moves before making your choice rather than jumping at the first thing you see.
4. What do you think your opponent will do next?
Yet again, usually no answer beyond “Dunno”. Thinking ahead wasn’t something they were yet able to do in any meaningful way. Fourth lesson: you need to develop depth of vision, to look ahead, to calculate, to assume your opponent is going to play a rational move rather than fall for your trap.
Young children under, say, 1000 strength, will find this way of thinking doesn’t come naturally to them. If they’re doing chess intensively at home, they’ll eventually get the idea, but if they’re only playing once a week at school they won’t. It’s difficult for most young children to use these thinking skills without specific training. But, to a certain extent, the questions apply to all players of all ages and at all levels up to, well, certainly 1500 and arguably 2000 strength.
For a lot more on children’s thinking skills in chess, I’d direct you toarticle I wrote almost 20 years ago.