Teachers in Cranston, Rhode Island, have filed a lawsuit against the city's school department, alleging their requests to observe Good Friday have been deliberately denied.

About 200 teachers contacted the union to report that they were being prevented from taking the day off, although they had provided more than the contractually required 24 hours' notice, said Liz Larkin, president of the Cranston Teachers Alliance.

On the other hand, teachers' requests to observe the Jewish holiday of Rosh Hashanah in the fall were approved, Larkin said.

"That's my big concern here, is equity," Larkin said.

The suit filed Monday is the latest legal battle over religion in Cranston schools.

In January 2012, a federal judge ordered a prayer banner at a Cranston high school removed after the state chapter of the American Civil Liberties Union sued on behalf of student Jessica Ahlquist, an atheist. The judge's ruling that the banner was unconstitutional set off a storm of criticism of Ahlquist, who received anonymous threats and scorn from lawmakers.

Kevin Daley, the attorney representing the union, said the teachers' collective bargaining agreement allows them to take up to two days off per school year to observe religious holidays. Daley said the contract does not specify restrictions on religious observances.

"They can take them if there are required services that take place during the school day," Daley said. "And Good Friday is regarded by Christians as certainly the most solemn of days of the church calendar."

Teachers who requested to take off the holiday, which falls on April 3, were asked to submit documentation of how they would observe it, Larkin said, but those who did were still denied.

School Superintendent Judith Lundsten did not return messages seeking comment.

Lundsten is one of several defendants named in the lawsuit, along with the school department and the school committee.

The committee voted in June to hold classes on Yom Kippur, Rosh Hashanah and Good Friday. Up until then, these holidays had been observed by schools in Cranston.

Larkin said she would like the committee to reinstate the holidays.

"This is the first year in many in decades that they have not been in the calendar," Larkin said.

Tim Ryan, executive president of the Rhode Island Schools Superintendents Association, said the school committee was trying to do the right thing by rescinding the holidays, fitting more school days into the calendar.

"We've had challenging weather," Ryan said. "Every day is precious."

Good Friday is a "traditional holiday," Ryan said, rather than an "official holiday."

Larkin said she is fascinated that the school committee, which fought to keep the prayer banner up, would vote to rescind the religious holidays.

A hearing has been scheduled for March 30.