Except in this case the mistake is that the government is willing to guarantee huge loans made to an 18-year-old. There are colleges out there that you can graduate with only a couple thousand dollars of debt and there are other colleges where you can graduate with hundreds of thousands of dollars of debt.
A potential fix would be to limit the amount of government-backed student loans to something people can reasonably pay off. If students want to go beyond that, they would need to convince a bank that funding the more extravagant tuition was a reasonable risk to take. With the government-backed student loans, you rely on an 18-year-old to accurately do the risk analysis themselves and the current situation seems to indicate many aren't good at doing this.