Chicago Public Schools is floating a plan to phase out one of its most popular magnet schools.

LaSalle Language Academy magnet school in Old Town gets 1,500 applications a year for around 70 openings.

Now, CPS wants to slowly convert the magnet to a neighborhood school that draws from the immediate area, one of the ritziest in the city. The school would take no new magnet school kindergartners in the fall, unless they already had a sibling enrolled in the school. Instead, the kindergarten would be filled with neighborhood children.

The change would relieve overcrowding at nearby Lincoln Elementary, where rising test scores have made the school a popular option for Lincoln Park families.

But LaSalle parents say the change would also dismantle their school’s diversity, achieved from 30 years as a desegregation school.

“You’re dramatically going to alter the nature and the demographics of the school,” says Tom Brennan, parent of two children at LaSalle and co-chair of the local school council.

Brennan says the proposal would be a particular loss to families from neighborhoods without great schools. He said families come from as far away as 85th and Escanaba and the Montclare neighborhood to attend LaSalle.

“They will not have diversity, a strong academic tradition, and other cultural, positive things that are not available to them in their current local school area.”

Observers and even some CPS estimates show enrollment at high-performing Lincoln and LaSalle schools would become overwhelmingly white. An internal CPS document obtained by WBEZ shows the district estimates LaSalle could shift from its current racial makeup of 33 percent white students to 63 percent white students.

The document estimates Lincoln Elementary would also educate a greater percentage of white students. Currently, 63 percent of students at Lincoln are white; 69 percent of students in what would be Lincoln’s new attendance area are white.

The plan would have violated Chicago’s desegregation agreement, which a judge ended two years ago. Since then, six more schools have become majority white, bringing the total to 25. The district overall is 92 percent minority.

CPS wants to add more magnet school seats at a school in West Town, LaSalle Language II, to compensate for those the city will lose at LaSalle.

CPS is presenting its plan to schools Tuesday evening. It wants the Board of Education to vote on the proposal in January or February.