The University of California came under new pressure Tuesday to eliminate the SAT and ACT as an admission requirement, when several groups threatened a lawsuit alleging that the tests violate state civil rights laws by unlawfully discriminating against disabled, low-income and underrepresented minority students.

A letter delivered to UC regents by lawyers representing the Compton Unified School District, the Community Coalition and others demanded that the university “immediately stop this discriminatory practice” or face litigation. It marks the first step in what could be the nation’s first lawsuit seeking to end the use of the controversial tests, which have been dropped as admission requirements by more than 1,000 colleges and universities across the nation, including the University of Chicago and the University of San Francisco.

UC spokeswoman Claire Doan said the university had no immediate response to the letter.

ACT and the College Board, which owns the SAT, took strong exception to charges that their tests are discriminatory. They said that differences in test scores reflect social inequities in access to quality education, not their exams. They argue that their tests are predictive of college performance and offer a uniform yardstick that allows colleges to compare students across a range of states and high schools.

“The ACT test is not discriminatory nor biased,” ACT spokesman Ed Colby said in a statement. “Blaming standardized tests for differences in educational quality and opportunities that exist will not improve educational outcomes.”

College Board spokesman Zachary Goldberg said the organization would continue to work with UC officials to promote student success but said the letter “contains a number of false assertions and is counterproductive to the fact-based, data-driven discussion that students, parents and educators deserve.”

Critics, however, say the exams are an unfair admission barrier to students who don’t test well or can’t afford to pay for pricey test preparation. Decades of research have shown that scores are strongly influenced by family income, parents’ education and race.

“Our objective is to remove barriers and equalize the playing field,” said Micah Ali, Compton school board president. “This is an issue of equity and access to opportunity for children who are living in marginalized and struggling communities.”

Any decision by UC to drop the SAT and ACT would play an enormous role in the future of standardized testing in America because of its size and status as the nation’s top public research university system. California is the largest market for the tests, and six of UC’s 10 campuses, which collectively educate 222,500 undergraduates, receive the most applications in the nation.

“This case is profound and far-reaching in its implications,” said Bob Schaeffer, public education director for FairTest, the National Center for Fair and Open Testing, which has fought to end the tests for decades. “The whole world will be watching.”

The UC Academic Senate, which sets the system’s admission requirements, is studying whether to drop the tests and plans to issue its recommendations to the regents by February. Doan said Tuesday that UC officials would wait for that review, requested last year by President Janet Napolitano, before deciding on the next steps.

“We understand the pressures ... particularly when so many of our young folks might be affected by the way in which we provide access to UC,” said Eddie Comeaux, co-chair of the Academic Senate task force on standardized testing.

“But whatever we decide we want to get it right and we want to be able to use evidence to support whatever direction that we decide.”

Several regents have expressed impatience to get on with the debate. Board of Regents Chairman John A. Perez has cautioned against “analysis paralysis.”

The demand letter, a legal precursor to filing a lawsuit against the system, also said students can’t wait.

“This is not a discretionary policy decision; it is a legal obligation and it is urgent,” the letter said. “The use of these exams is an unlawful practice ... and it is barring our clients from equal access to higher education.”

Kawika Smith, a senior at Verbum Dei High School in Watts who is one of three students threatening litigation, said that standardized testing requirements are stymieing his dreams to get into a good college. He has a 3.56 GPA, three associate degrees from L.A. Southwest College and a resume of leadership posts and community service.

But he said he and his mother, a home-care worker who earns just $23,000 annually, have struggled with bouts of homelessness and hunger and can’t afford private tutors or elite test prep courses. SAT training offered by his school and nonprofits has not been effective in teaching him key test-taking strategies, he said. Moreover, he added, he bombed several SAT practice tests because he had no money for breakfast and couldn’t concentrate on an empty stomach.

He’s resigned to low scores when he takes the test later this year and worries his performance will probably shut the door to dreams of getting into UCLA or UC Berkeley. (Standardized test scores are one of 14 factors that UC considers in admissions decisions.)

“I won’t be a competitive student, even though the SAT doesn’t give a true account of my potential,” Smith said.

The demand letter was sent by Public Counsel, a Los Angeles-based pro bono law firm, and four other legal firms and nonprofits on behalf of the three students. The groups also include the Dolores Huerta Foundation, College Access Plan, College Seekers and Little Manila Rising, among others.

They argue that standardized tests also discriminate against English-language learners, who may not be able to process word problems as quickly as native English speakers. And students with disabilities are also disadvantaged, they assert, because not all SAT test sites offer Braille, certain time extensions, or extended or extra breaks.

The myriad barriers result in huge disparities in scores, the letter said. Last year in California, 53% of Asian Americans and 44% of whites scored above 1200 — the 75th percentile — compared with 12% of Latinos and 10% of blacks.

ACT and College Board officials said their organizations work to address inequities by providing fee waivers to low-income students and free access to test preparation. ACT, Colby said, provides livestream tutoring, an online test practice program, support to English learners and accommodations to students with documented disabilities.

Mark Rosenbaum, a Public Counsel attorney, said his clients want to end all testing requirements — not simply make them optional as other universities have done.

“ ‘SAT optional’ is no more acceptable than ‘racially discriminatory optional,’ ” he said.

Christopher Edley Jr., a UC Berkeley law professor and co-founder of the Opportunity Institute, a nonprofit advocating educational equity, said the timing is right for a legal challenge because a less discriminatory alternative to the SAT and ACT now exists. The Smarter Balanced test is used in California and more than a dozen other states to assess how well K-12 students have mastered English and math skills required by standards known as Common Core.

Edley said he favors that test because research has shown it performs as well as the SAT in predicting first-year college grades with less bias against disadvantaged students. Another advantage is that 11th-graders at all public schools already take it during school hours at state expense. He added that the SAT is designed to produce low, middle and high scores. All students could do well on Smarter Balanced if they master the content California educators have determined they need to know.

If UC moves to Smarter Balanced, affluent parents could still buy their children test prep courses. But Edley said civil rights laws can’t eliminate all upper-class advantages.