A better idea is to make it like Social Security. You go for 60 hours on the taxpayer dime. Then, over the lifetime of your earnings; whatever you spent, you pay back with it taken out of your paycheck.
For example, if you're a 40+ y/o file clerk who wants to make more money, go to school for a few years and get a certificate in truck driving, X-Ray technology, welding, whatever.... You do this using government vouchers and lets say you spend $180 per semester hour. $180X60 is $10,800. Add in another $4,200 in books, fees, etc to make it an even $15,000. Once you're out of school for 6 months, Uncle Sam starts deducting money from your paychecks. Presumably you're making more so you're able to afford the deductions. At the age of 45, you have 15 years of employment or so left. Maybe more, maybe less. So your payments may be a bit higher than someone who is 18 y/o who takes advantage of the plan. Each month, your deduction is $90.00. At the end of a year, you've paid back $1,080. That amount is deducted monthly for the next 15 years and you've paid back $16,000+ on your $15,000 loan As you elevate in your career and get raises and what not, you miss the $90 less and less.
"Deferred Gratification" Means Deferred Growing Up
What is the clerk going to live on when he has to quit that job and go to school?
The clerk has to quit the job?
Problems from home: Those already in the work force as adults usually have responsibilities - kids, parents, child support, etc., and those living pay check to pay check or out of work are struggling before they decide to spend time on something that doesn't pay off in the near term.
Problems with small class load (like, one class per semester):
If you take one class at a time:
120 credits required for graduation, 4 credits per semester, 2 semesters per year. You do the math. In some cases, summer semester can reduce the time to, say, a decade. However, someone who has been out of school probably needs summer semesters just to fill deficits.
Plus, classes in your major almost never count toward graduation if they are more than 5 years old. They don't really care what you did 5 years ago - let alone a decade ago.
So, you just don't have 10 years to graduate. STEM departments won't accept you, or they will boot you regardless of your grades, if you get in, but progress anywhere NEAR that slowly.
Most universities have course work in STEM majors laid out in lock step. If you get out of sequence, you just lost a year. And, progressing usually requires courses in other subjects - math, for example. So, keeping up with the sequence by taking one university course at a time usually isn't possible - even if some school would let you try.
We have added money to education to bring along those who have deficits - night school, remedial math (like, for those not getting calculus in high school, not getting the foundations of biology in high school, etc.). But, those courses may not count toward graduation.
We could do more of that, but it won't be free, because it takes space, equipment, educators, management, etc. And, we should figure out what we're actually doing, because in science a 4 year degree earned over 10 years is ... what?