Just get rid of student loans.
This would do the exact opposite of improving access to higher education, which is the primary reason these higher costs are a problem in the first place.
The rising cost of education is little different than the rising cost of health care, and one problem they both share is a lack of transparent information. The federal government has the ability to track the ROI for every college degree from every university. They could give a salary histogram for each university for each major. They could allow prospective students to see how A student do in the workplace vs C students. They could see how students from a $200k+ household perform vs students from a poorer household. Armed with a true ROI, students could actually price shop for colleges.
Potentially more importantly, banks armed with this information could set interests rates more appropriately. Interest rates for engineering majors would likely be different than for philosophy majors. The government could subsidize certain majors if they felt it was in the public's best interests, but once again it would be transparent.
The idea that the market can be efficient without a decent level of public information is just silly.