For example, apps that run directly on mobile platforms (specifically, ones that don't need to connect to the 'cloud' to do their compiling):
- For iOS: Codea [1] (Lua), Continuous [2] (.NET), Swift Playgrounds [3] (Swift), Play.js [4] (Node.js + React Native) plus probably more (on that note, I really hope Continuous isn't abandoned, but it doesn't seem to have been updated in awhile).
- For Android: AIDE [5], TIC-80 [6], probably others (I'm not as familiar)
Moving up from mobile, you have FUZE4 Nintendo Switch [7] for the Nintendo Switch (excellent, but needs a bugfix update as there's lots of little annoyances). Probably the most kid-friendly thing there is right now IMHO, if you take into account the platform.
On the PC, there's just a huge amount of stuff. Minecraft [8], GameMaker [9], GDevelop [10], Godot Engine [11]. These are at least suitable for early teens.
[1] https://codea.io/ [2] http://continuous.codes/ [3] https://www.apple.com/au/swift/playgrounds/ [4] https://playdotjs.com/ [5] https://www.android-ide.com/ [6] https://tic.computer/ [7] https://www.nintendo.com/games/detail/fuze4-nintendo-switch/ [8] https://www.minecraft.net/en-us/ [9] https://www.yoyogames.com/gamemaker [10] https://gdevelop-app.com/ [11] https://godotengine.org/
Note: Yes, obvious game-making bias here :)