A federal judge on Wednesday set an expedited schedule for a trial on a discrimination lawsuit filed by Asian and white parents challenging temporary changes to how Boston admits students to its three exam schools.

U.S. District Court Judge William G. Young ordered the parties to meet and attempt to reach an agreement on undisputed facts by March 15 so that Boston Public schools can send students invitations to enroll in Boston Latin School, Boston Latin Academy and the John D. O'Bryant School of Mathematics and Science in late April. Those notices are usually mailed in mid-March.

A group called the Boston Parent Coalition for Academic Excellence, formed in November, last week filed a lawsuit against the Boston School Committee alleging its plan to use zip codes in determining most admissions to the three schools discriminates against white and Asian students. The lawsuit charges zip codes are used as "a proxy for race and ethnicity, so as to artificially favor Latino and African-American students to the detriment of Asian and white students."

Asian and white students have comprised an outsized majority of enrollment in city’s prestigious exam schools, particularly at Boston Latin, compared to their overall presence in the city's public schools. That imbalance in a school system where about 80 percent of students are Black or Latino has been a source of frequent complaints about racial-ethnic equity.

Last October, the school committee voted not to use a standardized exam to help determine admissions because the test could not be given during the pandemic. Instead, the distict decided to use a combination of GPAs, MCAS scores and zip codes, starting with neighborhoods with the largest number of school-aged children. Projections presented to the committee showed the numbers of Black and Latino students at the exam schools would increase under the plan.

A group of local organizations representing people of color, led by the Boston branch of the NAACP, this week sought to intervene in the lawsuit. Young allowed them to do so.

“The highly selective public schools belong to all Bostonians regardless of race, class or zip code," said Beatriz Abascal, coordinator of the Greater Boston Latino Network, in a media statement from the intervenors. "We urgently need to diversify and democratize access to the highly selective public schools.”

The judge did not rule on the Boston Parent Coalition's request for a temporary injunction blocking the school department from implementing the plan. He indicated he would rule on that request before April 15 after a trial. "I'm operating in an expedited way," Young said.

Kay Hodge, a lawyer representing the school committee, told Young sending the exam school invitations could be delayed until after April 15.

Young suggested there appears to be little disagreement among the parties about the the details of the department's plan and its demographic effects on the exam schools' enrollment, possibly avoiding the need to call witnesses and present evidence. In that case, he indicated he would rule based on the Constitution and law.

"I don't see any great disputes" about the facts, Young said. "The basic facts are known."