Yes, I think it is harder to ask appropriate questions at a high-school level. But I don't think it's because of the subject matter - I've answered several questions about how percentages work, and they seem to have been received just fine. I think it's because we expect the posters to have spent some time working on and thinking about their questions before they post, and most high-schoolers haven't yet learned how to do that.
I don't know if these distinctions will mean much to you, (they're college-based), but posting here isn't as formal as going to ask the professor, but it's more formal than going to the tutoring center. Think "going to ask the official class T.A.".
So if you want to just throw out questions, muse about them, and kinda kick the sh*t around, that won't work here and you should look for something more reddit-y, or a Discord channel, for that.
But if you find some question really getting to you, and you've thought about it five different ways and want to spend more than 2 minutes writing up what you've got, there are some really smart and talented people who answer questions here, and it can definitely be worth your effort to get their input.
Edited to add: Oh, wait, I totally forgot about the chat rooms! You do need 20 rep to participate, and 100 rep to create a new one (h/t @MartinSleziak),but they are much more free-form. Of course you don't get the same level of exposure or expertise as posting to the main page gets you, but maybe a good strategy for you is to try things out in chat rooms, and if people there don't have answers, y'all can formulate good questions that will work well on the main site.