i'm not saying it's not possible... but we're talking about teaching kids... there are few of them enjoying to go deeper and getting even more interested when things get more complicated , despite the lack of actual positive results during the process (i guess it was your case as well) , but the majority of kids are like "does it work in 10 minutes ? no ? that's boring shit, i rather try something else".
btw... when i was a kid/youngster i was coding Z80 and 8080 without using assembly - directly writing code in hex-editor ( a hex editor written by myself) just because i was able to do it and it was much faster than writing the code in assembly and then compile
but i'm not expecting that everyone else is able to do it, and i'm not even suggesting to do it that way - because for the majority of people it's way too complicated to learn all the opcodes for the whole instruction set (and in fact it's waste of time to learn that).
so the fact that one person is able to do something doesn't mean that everyone should do it that way, and it definitely doesn't mean it's the right way of doing that thing...
so in fact the RPi is close to ideal for teaching kids how to interface HW - you get everything you need - a small computer with OS a highlevel language interpreter and libraries for easy manipulation of the GPIO pins. the kids are able to make a LED go blinky-blinky in 5 minutes (hook-up the RPi to a breadboard, stick in a led + resistor, write very few lines of python code and bob's your uncle), they'll see an actual result very quickly and there is a bigger chance that they'll get interested even more and dig deeper.