Raleigh, N.C. — Some community leaders said Monday that  the pressure to find seats for thousands of new students could disrupt the racial and socio-economic diversity of Wake County classrooms.

The Wake County school system sent letters last Friday to the families of about 32,000 students, asking for their permission to send the children to year-round schools. Anyone who doesn't return the letter by Friday will be assigned to a traditional-calendar school.

The school district plans on converting 19 elementary schools and three middle schools from traditional to year-round calendars, saying it needs the extra space to accommodate a projected 8,000 new students.

A group of parents sued to block the move, and a judge ruled that the district couldn't assign students to a year-round school without parental consent.

More than a dozen African-American community leaders and clergy urged parents to sign and return the letters, saying year-round schools are important to maintaining diversity at a number of Wake County schools.

"We're here to stand for what's right," Michael Leach, president of the Raleigh-Apex chapter of the National Association for the Advancement of Colored People, said at a Monday morning news conference. "The NAACP supports a school system designed for all people."

The Economist magazine recently highlighted Wake County as a leading example of school diversity. But some community leaders said they fear the district will backslide if too few parents elect year-round schools, forcing more students into traditional schools that are already overcrowded and creating more segregation.

"My fear is that we could move back to segregated schools in a while," said Alice Garrett, a retired teacher and chairwoman of the Raleigh-Wake Citizens Association. "One segregated school in a county is one too many."

"This is a matter of ethics beyond ethnicity. This is a matter of principal beyond interest," said the Rev. Joe Stephenson, the pastor of Macedonia New Life Church.

Classroom diversity remains important to district officials, spokesman Michael Evans said, but it is only one factor in school assignment.

"It has become harder and harder (to balance) because of the growth in general. We do not live in a socio-economic integrated community," Evans said.

Parents who opt for a traditional school, by either choosing it on the letter or declining to return the letter, won't find out until at least mid-June where their children will be assigned.

"It is critically important that black parents do not neglect to return the the forms to their current schools.," school board member Rosa Gill said. "Leaders would like as many people as possible to choose the year-round option, but even if they want to remain in traditional-calendar schools, the forms still need to be returned to voice their choice to remain where their children are now."

District officials said they expect at least two-thirds of the families receiving permission letters to accept year-round assignments.