Many high school students in Maryland have been able to lighten their academic load during senior year by taking a break from tough math courses.

But that’s about to end.

Starting with the Class of 2015, 12th-grade math is required for seniors who are seeking admission to Maryland’s system of public universities. Separately, all students in Maryland will soon be required to take math every year of high school in order to graduate, a change that will start with next fall’s

The changes come from state law and admissions policies meant to increase rigor and better prepare students for college and careers.

As across the country, concerns have intensified in recent years in Maryland about college freshmen increasingly needing remedial math to get up to speed before they can enroll in true college-level math courses. Even if students don’t need remediation, many lose ground by skipping math in later years of high school, experts say.

In Maryland, graduation requirements now include three years of high-school-level math. Locally, Prince George’s County adheres to the three-year requirement, and Montgomery County requires four years. But in Prince George’s and Montgomery, many students start high-school-level math in middle school, so they are able to fulfill their high school requirements long before senior year.

With the new requirements, math will be a constant through high school.

“There’s not the opt-out option anymore for anyone in Maryland,” said Jack R. Smith, chief academic officer for the Maryland State Department of Education. As with foreign language, Smith said, math is highly sequenced and important to keep up with, which is why state officials want seniors to continue taking it.

“You stop doing those things, you lose them,” he said.

Maryland educators praised the new mandate.

“You’ve got to stick it out now,” said Ed Nolan, director of the mathematics implementation and development team for Montgomery’s schools. “We don’t want them to take time off. The more math they take, the better and deeper and richer their understanding,” said Nolan.

Gladys Whitehead, director of curriculum and instruction for Prince George’s schools, said the district has been urging more math during high school.

“I think it blends in with the whole movement of Common Core and preparing them to be career- and college-ready,” Whitehead said, referring to the new national academic standards that Maryland has adopted.

With the old requirement, Whitehead said, students who started algebra in seventh grade could have left math behind after ninth grade, making them less prepared for college or career opportunities after high school. “After you haven’t had math for three or four years, it’s hard to show your best work,” she said.

Officials in Prince George’s did not have data Friday about the number of students who decide to forgo math in late high school years because they had already met their graduation requirements.

In Montgomery, more than 90 percent of about 21,000 11th- and 12th-graders took math as juniors and seniors each of the past three school years, according to district estimates. But about 1,150 Montgomery students skipped math last school year.

“I’m hoping they will be better prepared for whatever that next step will be after high school,” Nolan said.

A recent look at math remediation rates at Maryland’s community colleges and public universities showed that more than 55 percent of 31,000 Maryland high school graduates needed the catch-up courses.

The new graduation requirement — stemming from legislation passed last year — follows similar thinking from the University System of Maryland Board of Regents, which voted in 2009 to require four years of math for its 11 institutions.

Under the university system’s requirement, students need to have completed at least four years of high school math, including a senior-year course that uses “non-trivial algebra.” Examples include Algebra 2, trigonometry, pre-calculus, calculus, statistics and college algebra.

Theoretically, students who start high-school math in middle school could skip the subject junior year — if they resume it senior year, said Board of Regents spokesman Mike Lurie.

The first to encounter the requirement, he said, will be today’s juniors, many of whom expect to apply to college this coming fall. Without a senior-year course, “they get rusty,” he said.

Nationally, starting with the Class of 2013, there has been an increase in the number of states requiring four years of math. Now, 17 states and the District have that requirement, said Jennifer Dounay Zinth of the Education Commission of the States.

In Virginia, the standard diploma requires three years of math. The advanced studies diploma requires four years.

Michael W. Kirst, professor emeritus at Stanford University, said his greatest concern is about lower-performing students. “A sequenced four-year math program is very important for college preparation,” he said.

But the nature of the courses is key, he said. “It has to be designed well.”

Some are not convinced that the changes would significantly resolve the need for remedial courses in college.

“It will help a little bit,” said Jerome Dancis, associate professor emeritus of mathematics at the University of Maryland in College Park. But much of the trouble learning math occurs early on.

“Students who are on the track to end up in remedial math will still end up in remedial math.”