Looks like an excellent guide, even for adults!
The fact that each subroutine has its own dedicated window really helped me to create my first complex program when I was young. Type F2 to access any routine directly. A program was a set of subroutines rather than a set of lines.
There was an online help too, and a survival guide.
You can try it out here: https://www.pcjs.org/software/pcx86/sys/dos/microsoft/5.00/ . It will launch MS-DOS 5 on a PC/AT. Type QBASIC to launch it.
Also, as a non-native speaker (and a computer hobbyist, not an educated IT guy), I would point out that the language of this guide seems really-really good.
The author seems to be a collector of old computer books for kids as well [1] -- this very probably also contributes to why his QB guide feels so well polished. The author very successfully avoids overwhelming the kids with programming terms; he is really careful in introducing those. Also, the sentences are simple, short and to the point; and somehow... warm, empathetic towards the (learning) child.
I'm actually in the process of translating this to my language (Estonian), and going through the exercises simultaneously with our 10yo son. I think we're doing great! That Blue Screen of QB really helps in maintaining a child's focus. QB is a notably good IDE for kids, maybe almost unbeatable in this regard even in 2023?
1: http://tedfelix.com/books/index.html and http://tedfelix.com/cs4kids/index.html
2: see also the author's additional tutorial, Sprites in QBASIC: http://tedfelix.com/qbasic/sprites.html