What you're essentially asking for is to create two separate classes of people. Your idea would result in us regressing back to the idea of 'philosopher kings' and I would hope I shouldn't need to argue why that's a bad idea.
People should be able to get an education no matter their social standing. It shouldn't be tied to this idea of job prospects because commodification of education is a sham.
If educacation doesn't have some sort of monetary value what is the point? Entertainment is a valid answer, but it should be in different bucket.
I did not not in any way say that some people shouldn't be able to get an education. I said if the education isn't valuable they shouldn't get one, but there are many valuable education paths to take.
Why does everything need a monetary value? If someone wants to be an artist, that doesn't necessarily come from a world of wanting to make money from their art.
And who defines whether or not an education is valuable? Teachers don't have very good job prospects (low pay means they're less valuable), do you think it would be a really good idea to restrict who can become a teacher to only the reasonably well off?
Teachers should not be paying full price at Harvard (I don't know if Havard even offers a teaching degree), there is value in a teaching degree but only enough for the much cheaper state schools.
I have no problem with people wanting to be artists. The world needs art. However I have a problem with someone spending more than they can afford on anything. Want an art degree, first get a job and save up as art will never pay the bills (there are exceptions that prove this rule). Once you can afford to live (that is eat and a tiny home: the minimums) go ahead and get whatever luxury you can afford. Some get an art degree, some a nice car, some collect stamps, you can have a family. I don't care much what you choose so long as you are not beyond your means.
To put it a different way, if you are making an investment then it needs to be a good investment with a return on investment. If you are not making an investment that is fine but then you need to be careful not to destroy your future on bad choices.
People should be able to get an education no matter their social standing. It shouldn't be tied to this idea of job prospects because commodification of education is a sham.