WASHINGTON (AP) _ Early exposure to serious math, algebra and geometry, opens the gate to college for large numbers of students, including minorities and those from low-income families, an Education Department report says.

The report, ``Mathematics Equals Opportunity,'' was released Monday by Education Secretary Richard Riley, who said it offers evidence that the choice of subjects determines access to college, not whether the school itself is public, private or parochial.

``These courses demand discipline, they demand hard work and they demand responsibility,'' Riley said as he unveiled the new report in a ceremony at the Old Executive Office Building. ``They make a powerful difference in terms of going to college.''

The problem, he said, is that only about 25 percent of U.S. eighth-graders enrolled in algebra classes last year.

President Clinton took the report as a new reason to support his proposal for voluntary national tests of reading in the fourth grade and math in the eighth grade ``to ensure that all our children meet the high standards of academic excellence they'll need to succeed in tomorrow's world.''

Many Republicans oppose such testing, and Clinton said: ``I call upon Congress to end the delays. Our children are counting on us.''

Riley said that by proposing the tests, Clinton is ``laying down a challenge to shake up the status quo.''

``If these critics are going to be serious about improving American education, I would urge them to read this report and join us in this call for higher standards,'' Riley said. ``Sometimes you need to put politics aside and get serious about education.''

``The voluntary tests will focus like a laser beam on making sure we get the basics right,'' he said.

The report had three central conclusions:

_Eighty-three percent of young people who go on to college take ``the important gateway math courses,'' starting in the eighth grade. Riley said: ``That is a very important finding that goes against the conventional wisdom that a family's status and income are the determining factors.''

_Low-income students who took algebra and geometry were nearly three times as likely to attend college as those who did not. Seventy-one percent of those who took such courses went on to a higher education.

_Taking these courses is more important than the type of school attended. The report suggested that students in public and private schools who took rigorous math and science classes were equally likely to score in the highest levels of 12th-grade math tests.

Many Congressional Republicans contend that giving parents tax dollars in the form of vouchers to shift their children out of public schools and into private or parochial schools is the answer to improving their education.

``The report says that there is a much more important choice that is being overlooked entirely and that is the choice of courses,'' Riley said.