The U.S. Supreme Court struck down President Joe Biden’s student loan forgiveness plan Friday, yet college affordability will remain an issue for years to come, experts say, causing more students to opt out altogether.Given the Supreme Court’s ruling against affirmative action admission policies as well, “it’s very appropriate for us to be concerned,” said Kelly Slay, assistant professor of higher education and public policy at Vanderbilt University. “Instead of broadening opportunities, we’re adding barriers.”Michele Shepard, senior director of college affordability at The Institute for College Access & Success, added that “this debt-financed system is unsustainable.”More from Personal Finance:Supreme Court strikes down student loan forgiveness plan4 strategies to avoid taking on too much student debtThese moves can help you save big on college costs”We continue to be concerned that the high cost of college — including not only tuition costs but housing, food, transportation and other living costs — is giving students second thoughts about enrolling,” she said.College is only getting more expensiveTuition and fees have more than doubled in 20 years, reaching $10,940 at four-year, in-state public colleges, on average, in the 2022-23 academic year. At four-year private colleges, it now costs $39,400, according to the College Board, which tracks trends in college pricing and student aid.”The [Supreme Court] decision still does little to erase the massive burden brought on by the exponential rise in college tuition,” said Sarah Foster, analyst at Bankrate.com.Many students borrow to cover the tab, which has already propelled collective student loan debt in the U.S. past $1.7 trillion.Typically, seven in 10 college seniors graduate in the red, owing an average of nearly $30,000 per borrower, according to the most recent data from The Institute for College Access & Success.This year’s incoming freshman class will rely on loans even more in pursuit of a degree at a public college or university, a recent report shows.A 2023 high-school graduate could take on as much as $37,300, on average, in student debt to earn a bachelor’s degree, according to a NerdWallet analysis of data from the National Center for Education Statistics.The share of parents taking out federal parent PLUS loans to help cover the costs of their children’s college education has also grown, NerdWallet found.A wave of students may opt out of collegeBetween the high cost of college and student loan burden, students are increasingly questioning the value of a four-year degree.”I started looking for a path that would be the cheapest and cause the least amount of debt,” said Parker O’Neill, 18, who will start a two-year dental assisting program this fall at Century College, a community and technical college in White Bear Lake, Minnesota. Watching his mom struggle with her own debt repayment was the determining factor, he said.High schoolers are also putting more emphasis on career training and post-college employment, a recent report by ECMC Group found.About two-thirds, or 65%, of high schoolers think education after high school is necessary, the report said, but among students from low-income, first-generation or minority backgrounds, only 47% are considering a four-year college. How to avoid taking on too much student debtWith debt relief off the table, “people now should realize they need to be prudent,” said Kalman Chany, a financial aid consultant and author of The Princeton Review’s “Paying for College.” High-school students must plan ahead, he said, by maximizing gift aid, such as scholarships and grants, which does not need to be paid back; choosing schools that are affordable; and not borrowing more than they expect to earn in their first year after college.Above all else, would-be students should “be very careful with how much they borrow,” Chany said.Subscribe to CNBC on YouTube.