The Little Rock schools, center of the nation's first confrontation between the federal and local governments over desegregation 24 years ago, are proposing a plan that would put half of the system's youngest black students in totally segregated classes, its superintendent said yesterday.

Superintendent John Masem said that the city School Board voted, 4 to 3, last week, over the objections of its lawyers and himself, to take the proposal to a federal judge today. The 20,000 student system is about 65 percent black, the reverse of what it was 10 years ago.

The plan would group white students so they make up 35 percent of each class. But because there is a higher proportion of black pupils in the lower grades than in the higher ones, "pretty soon you run out of white kids" in those classes, Masem said. He estimated that the effect would be that about half the black students in grades 1 through 3 would be left in totally segregated classes.

Board member Peter Sherrill, who introduced the proposal, told United Press International the move is necessary to keep the remaining white children in the system. "If the judge rules against it, I think there is a real danger of seeing those first three grades go almost entirely black and seeing the white community desert the public schools system."

Little Rock was a focus of national attention in 1957 when Arkansas Gov. Orval Faubus called out the National Guard to keep blacks from attending the city's Central High School. President Eisenhower sent in federal paratroopers to ensure the students could attend the schools safely.

The current desegregation plan in Little Rock dates back to court decisions in the early 1970s and involves cross-town busing for nearly all students. The busing wouldn't change under the board's proposal, Masem said, just the class assignments once the children arrived in school.

T.E. Patterson, the board's only black member, told UPI the majority was bowing to a small number of the district's parents. "I think saying that whites don't want their children in a class with large numbers of blacks is saying there's something wrong with blacks by connotation," he said.

Sherrill said, "I don't think the kids notice any difference at all. It's the parents who have the hang-ups. And it's the parents who can yank the kids out of school."

John Walker, the attorney who argued the case for a black parent, called the decision "insulting" and vowed to fight it.