My thought? E-waste.<p>This is how I got my first computers; obsolete and broken computers cast off by people wealthier than I was. [1] It's great, because you get to learn how to fix the computer as well as whatever it is you learn on the computer. I imagine my life experience is super different from those you are helping, but I can tell you that early experience fixing obsolete computers has vastly helped my career.<p>It <i>is</i> a lot more labor intensive, because you have to have someone to teach the kids how to fix the damn things, (for me, my dad and a copy of minasi's "upgrading and repairing PCs") but once you have that skillset locally? it's probably sustainable, because the rich will always be throwing out last years gadgets.<p>In some ways it will be way easier for you than for me; when I grew up in the '80s and '90s, there wasn't a lot of standardization, so with my 'catch as catch can' hardware acquisition strategy, I'd have to completely change my software stack every time I got new hardware. These days? Most educational software runs in a browser (I use and heartily endorse Khan Academy for the parts of learning that can't be done from a book alone) and so you can have a diverse fleet of hardware and even operating systems, and as long as you have enough local skill to bring the things up to the point where they can run a browser, you should be good to go.<p>The big problem with this plan is power; Nicer gear from the aughts ought to run a browser just fine, but it will chew up a lot more power. If you have to pay for unsubsidized electricity, more modern gear might make more sense.<p>[1]There was also this really juicy (for me) sense of acquiring "means of production" - I <i>owned</i> these computers that others had cast off as worthless or broken, and I turned them into a useful resource for myself. I think that if you could work something out so that the kid in question gets to keep the computer they fix... that might be extra gratifying. I know it was for me.