So basically you just described income tax
Except the school only gets the money of people who attend the school. And the school is not incentivized to sell worthless degrees because it won't get paid when it does.
Hmm well given how essentially all salaried jobs require a degree today it’s hard to see education as being an optional purchase for most people. Maybe 30 years ago but not today.
Hard to say what’s worthless or not - jobs change all the time. Few if anyone would study something like Latin or philosophy if money were an incentive.
Also the idea of human knowledge being locked away for only those who can afford it seems cruel to me