It’s an incredibly powerful and easy to use game/interactive-app maker that can export packaged programs to Windows, OSX, Linux, and HTML5, then with additional licensing/fees to game consoles.
It has a drag-and-drop mode for absolute beginners that can let someone with zero experience be creating simple games in their first weekend playing with it.
Then it has GML mode which is their programming language with excellent documentation and a decent community cranking out tutorials and guides, which has put out some seriously legit indie games such as Red Strings Club, Hyperlight Drifter, and Hotline Miami.
It’s also not just for games. It’s great for making interactive stories (I’ve made interactive kids books with it), HTML5 demos and interfaces, 2D physics demos, and even does basic 3D stuff.
(Not affiliated just a big fan and use it extensively).
But I would suggest Godot as an alternative for beginners now. Even though I don't like the proprietary scripting languages either uses by default, between GML and GDScript, the latter seems more powerful, and thus more educational. You can do "drag and drop and make a game for some defnition of a 'game'" in any of the modern game frameworks. But really, that only teaches you how to use the GUI, not how programming works.
Also Godot has a version that uses C#, and there are bindings for other languages out there (I don't know how complete or useful they are, though) whereas unless I'm wrong, with Game Maker you're stuck with GML.
I do hope to start publishing some children's games and educational interactive stories one day though, I just need to find an artist (or practice more myself).
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 :)