Three decades after Massachusetts fundamentally overhauled its K-12 public education system with more funding, higher standards and greater accountability for students and teachers, voters repealed a key provision of the landmark law that helped make the state’s schools among the best of the country.

Early Wednesday morning, the Associated Press said Question 2, the teachers union-backed ballot initiative to eliminate the state’s only uniform high school graduation requirement, would win with about 87 percent of the vote so far. Beginning with the Class of 2025, high school students would no longer be required to pass their Massachusetts Comprehensive Assessment System (MCAS) subject exams to receive their diplomas. Students would only be required to complete coursework that their district certifies meets the state’s academic standards.

The MCAS referendum was among five major policy decisions put before voters. Voters easily approved another statewide ballot measure, Question 1, that would authorize the state auditor to audit the Legislature’s books, but rejected a measure that would increase the minimum wage for tipped workers and opposed the legalization of certain psychedelic substances away.

A measure that would allow ride-hailing drivers to unionize had not been announced as of early Wednesday morning.

“The public has responded,” MTA President Max Page told his supporters Tuesday night during an election night party, when the referendum was still underway but had not yet been called. “They responded by saying, ‘I trust our educators, I trust our parents,’ and it was really nice to see.”

The campaign to eliminate the MCAS graduation requirement is the culmination of decades of frustration among many educators and parents over high-stakes standardized testing, fueled by the disruption of the COVID-19 pandemic that left many students behind academically and unable to catch up .

The MTA has argued that the requirement causes too much anxiety among students, unfairly penalizes poor test takers and is potentially discriminatory. They also say MCAS forces teachers to spend too much time on test prep and crowds out civics, art and other subjects. The union believes a more holistic approach to assessing students would provide more useful information about whether they are ready for college or the job market.

“I would be thrilled” if the measure passes, said Ann Civitareale, mother of two Medford High School students. Both sons have learning disabilities and had difficulty with their MCAS exams.

“They both work really hard and deserve degrees,” she said.

Opponents of the ballot question argued that the MCAS graduation requirement plays a critical role in moving Massachusetts schools from the middle of the pack to the top nationally and ensuring that graduates have basic skills in English, math and science.

Most students pass the exams on the first try. But each year, more than 700 — mostly English learners or students with disabilities — are denied diplomas because they couldn’t pass one or more MCAS exams, about 1 percent of all incoming high school graduates.

“For me, having ADHD and dyslexia, it gets to a really bad point, especially when I’m taking tests,” said 15-year-old Hanem Shabana, a sophomore at North Quincy High School.

The MTA outspent its opponents from the business-backed No on 2 campaign, investing more than $16 million in staff time and money, according to recent campaign finance disclosures, and garnering support from Democrats in Congress, including Senator Elizabeth Warren and Representative Ayanna Pressley.

By comparison, Protect Our Kids’ Future, the campaign against Question 2, raised more than $5 million. Democratic Gov. Maura Healey, Lt. Gov. Kim Driscoll and Attorney General Andrea Campbell also weighed in favor of maintaining the graduation requirement.

Deanna Pan can be reached at [email protected]. Follow her @DDpan.