Raleigh, N.C. — The Wake County school system cannot convert 22 traditional-calendar schools to mandatory year-round schedules this summer, a judge ruled Thursday.

Superior Court Judge Howard Manning's decision throws the district's plans for the 2007-08 school year into chaos, with only three months to find classroom space for an expected 8,000 new students, hire teachers and rework bus routes.

The school board called an emergency meeting for Friday morning to discuss its next move.

"Obviously, it causes a lot of concerns for us at this point," district spokesman Michael Evans said. "The board's going to walk through this step by step, and we'll come up with a decision that's going to be the best, given the circumstances we're facing."

The district approved moving 19 elementary schools and three middle schools to year-round schedules last fall, saying they needed the extra space provided by year-rounds to accommodate surging enrollments. Manning's ruling not only affects the 22 schools, but it affects any studetn who is currently assigned to a year-round or modified year-round school.

But a group of parents, organized as WakeCares, sued to block the move, contending that forcing them to switch schedules would be unfair to their children and would disrupt family life. The mayors of Apex and Garner backed the parents' group, saying their towns would suffer in year-round conversions and the district's decision deprives many parents of educational choices.

In a 35-page decision, Manning ruled that school districts can require students only to attend a traditional-calendar school. Any assignments to magnet or year-round schools must be voluntary, he said, citing a 2004 state law that said public schools should begin classes no earlier than Aug. 25 and end no later than June 10.

"The Wake County Board of Education lacks the statutory authority to convert traditional-calendar schools to mandatory year-round. Thus, the board of education may not require the attendance of students at year-round calendar schools without informed parental consent," he ruled.

About 20,000 families would have been be affected by the conversions.

"We'd like to thank Judge Manning for protecting the right of children to an equal-opportunity education," said Kathleen Brennan of WakeCares.

"The No. 1 thing that strikes me is never underestimate the determination of some mommas," Apex Mayor Keith Weatherly said about the parents' victory in the suit.

School district administrators said converting the schools is necessary to create enough seats for an expected 8,000 new students in the fall. Year-round schools can handle more students because students are separated into four groups with rotating schedules, with three in class and one on break at all times.

Without the conversions, schools might have to run on split schedules, with some students attending early-morning classes and others going to school in the afternoon and evening, district officials have said.

Manning's ruling opens the door to a possible legislative battle for the district, which could turn to lawmakers to obtain the statutory authority for the year-round conversions.

WakeCares members complained Thursday that district administrators didn't prepare a back-up plan in the event they lost the lawsuit. Now, they said, thousands of students and families are left in limbo as the district scrambles to make up ground.

"We are extremely sorrowful if this is going to cause any kind of problem for families that have made plans because we know what that is like," said Patrice Lee of WakeCares.

"This is a false crisis made up by the school system for whatever reason," Weatherly said.