Quick, what’s the value of x in 3x/2 + 5 = 20?

Don’t know?

If you’re rusty since it’s been a while since your last high school algebra class, we’ll forgive you for now. But if you’re a soon-to-be high school graduate celebrating your recent college decision, then we have some cautionary news for you and your parents: You may end up spending nearly $1.5 billion in extra college costs if you graduate from high school underprepared.

That’s the sobering reality facing many of today’s college first-year students. One in four who enter college immediately after high school graduation must pay college-level prices for high school-level classes.

Typically, underprepared students will be forced to enroll in so-called remedial college classes or more diplomatically-named courses like “Developmental English,” “Algebra Review” or “Introduction to Writing.” Most of these courses won’t count towards a student’s college degree. What that means is college will cost even more than these students and families realize.

But before you write off inadequate high school preparation as a function of a student’s family background or the type of college they attend, know this: Nearly half of first-year remedial students come from middle-class, upper middle-class and wealthy families. Forty percent are enrolled at public and private four-year colleges.

That was one of the biggest surprise findings in our recent analysis of national data from the U.S. Department of Education. We already knew that high schools typically underserve students from low-income families and communities, but apparently they’re doing poorly with wealthier students as well. It turns out that all students are susceptible to the leaky K-12-to-college pipeline – no one is immune. This should be a wake-up call for all.

The consequences are particularly acute for families making more than $115,000 a year sending their kids to expensive private nonprofit four-year colleges like the University of Miami, Northeastern or Wake Forest: Not only do they pay higher private school prices, but underprepared students also take more remedial classes than average. That means that they pay, on average, an extra $12,000 for content they should have learned in high school.

Now, this isn’t a finger-pointing exercise where the high school or the college or the student or the parent is exclusively to blame. Because the problem is so widespread, we must first demand public recognition and acceptance that this is a problem facing all of our kids – not “somebody else’s” kids who are suffering from mediocre high schools and unsuccessful colleges. Second, we must demand that every party work together and be held accountable for better results.

For instance, high schools need to become much more academically demanding. All high school students should be required – at least as a default – to enroll in a college prep course of study that is aligned with the requirements to enroll in introductory-level college classes. High schools should ensure that these rigorous courses are equally available and well taught to all students. Students who are struggling should receive additional assistance and mentoring.

Colleges need to change the way they identify and teach students who come in behind. They need to redesign the way they deliver remedial education and support services so students aren’t forced to pay extra for their inadequate high school education. Because by virtue of accepting a student and taking his or her money, the college must accept the obligation to deliver all the educational resources it takes to ensure that student succeeds.

Students and families also need to take ownership and responsibility for deeper engagement and learning in high school.

As it stands now, the typical bachelor’s degree graduate takes over five years instead of four to finish a degree. Those who come in behind and enroll in remedial coursework their first year are 74 percent more likely to drop out than those who do not need remediation. Those who drop out with debt are four times more likely to default on their student loans than those who graduated.

It’s time that we recognize that the college affordability issue – what some consider to be a crisis – is directly related to the fate of high school reform and high school student achievement.

So if you’re currently a high school senior eagerly anticipating graduation day and the college road ahead of you, make sure the college you selected is well-equipped to serve you. If you’re younger, take the time now to study hard and demand more from your teachers and school leaders.

Because imagine how more affordable college could be if all students were prepared for college coursework on day one, and were able to graduate on time. It would save students, families and taxpayers from the heartache of wasted time and money.

A version of this commentary originally appeared in U.S. News and World Report.