Conty. Economies are like a circulatory system. It's not like the govt. sets your tax money on fire - it sends it back out into the economy in myriad purchases of goods and services from the private sector, and govt. employees are also consumers in the market, and they pay income tax, too.
Your pre-occupation with a small percentage of students is disingenuous. That, or you should "stop tarding".
A taxpayer has an average adult earning lifetime of 30 to 45 years to pay income taxes, besides all the unavoidable consumer taxes. Even sad gits who work off the grid cleaning houses, buskering, begging, selling drugs, selling art for cash pay all the tax other than income tax in VAT, retail, tolls, vehicle tags, etc. The money that went toward a wasted education does in fact get recouped over time. And with normal folk, the return is very much faster.
Would you also do away with free schooling for ages 5 through 18? Are we to turn back the clock and assure the return of feudal culture? That would save your precious posh fucks a bit of money, but I hope they enjoy living in a fortress and hiring a team of body guards to avoid all the starving, the desperate, and the savage uneducated and disenfranchised hordes. Oh, yes, that already happens in all the places that have no middle class and a bought government. Some of the few good job sectors in those places include manufacturing bullet proof cars, piloting private helicopters, building hidden safe room enclosures in mansions and training attack dogs.