The government should simply stop protecting student loan debt from being discharged in bankruptcy. Then lenders will have to take responsibility for their lending actions, universities will have to lower tuition due to less "free" money, and students will have to be more careful with what field they choose.
Obviously students shouldn't be pursuing degrees that won't result in a well-paying job, but the lenders are still partially responsible. After all, if you ask a bank for a business loan with a stupid idea, the bank won't give you money, because they know they'll probably lose it. I don't know why it's different with education.