(1 teacher / 20 students) * ($50k / teacher-yr) = $2500 per student per year to fund teacher salary.
Compare that to $40/yr domain+hosting, which maybe 10% of students will use. $4/student-yr will not be the diffence between paying teachers probably or not.
But sure, yeah, there'd be some admin time spent managing it. As with anything, there are plenty of reasons not to do it. It struck me as a low cost-to-impact ratio thing that could get kids into tech, but reasonable minds could disagree.
It would result in rampant wildness and people complaining, but if you didn't do it that way the burden would be too high.
I was very happy about free TLDs back in the day as a teenager, since I could just try things out before having to convince my parents to let me use their credit card to register a proper domain name.
At a quick glance, many registrars and hosters seem to accept crypto, and anyone can buy prepaid Visa and Mastercard cards anonymously for cash for the ones that don't.