The Prince George's County school system, which has been criticized frequently for suspending a disproportionate number of black students, will soon begin sending many misbehaving pupils to special "study centers" as an alternative to suspension.

Instead of being sent home, the suspended students will be placed in separate classrooms with others judged behavior problems. There, they will be able to continue their academic schedules seperated from regular classes.

Sue V. Mills, the School Board member who originally proposed the alternative, said that students who commit serious offenses -- such as assault with a weapon -- will still be suspended entirely and that the new program will apply to less serious forms of misbehavior.

Officials expect the number of suspensions -- about 6,000 in 1976 -- to degets under way.

The controversy over suspensions stems from the fact that black students, who constitute about one-third of the total county enrollment, account for well over 50 per cent of those suspended. Last year, 57 per cent of the 6,000 students suspended were black, according to county statistics.

In 1974 the NAACP Legal Defense Fund sued the county, accusing it of depriving black children of their right to public education through discriminatory suspensions. The suit was settled out of court and the county distributed a statement clarifying what offenses warranted a suspension.

That statement, later called the student code of conduct, was not able to curb the number of black student suspensions, which continued to rise at a pace faster than that of white students.

At that time the head of the NAACP student suspension project, Eloise Hamilton, said: "What is evident is that the intent of the court settlement hasn't been realized." She and others who worked closely with problem of student suspensions in the county agreed that the student code was fair, but its application was not.

The current school superintendent, Edward J. Feeney, and other school administrators disagree with that assessment.

The "in-school" suspension program as the new system will be called -- is patterned after similar efforts in Fairfax County and Florida.

It is scheduled to begin operation shortly at Thomas G. Pullen Junior High in Landover, and at Roger B. Taney Junior High and Crossland High School, both in Camp Springs.

The special classes will be staffed by a teacher and a teacher's aide at each school.

"It is not going to be fun and games," said Mrs. Mills, who noted that suspended students will not be able to eat with their friends in the school cafeteria and that they will have an "escort" throughout the day. She said these students will not be able to participate in team sports or after-school activities and that they will have to keep up with classroom work.

Reasons for suspension range from "insubordination" -- which means anything from cursing a teacher to setting a pattern of disobedience -- to fighting.

Last school year there were 4,034 student suspensions for insubordination and 2,613 for fighting. Other categories in which there were large numbers of suspensions included loitering, with 1,702 suspensions, and classroom disruption, which accounted for 1,685, according to a report released last summer by the school board.

The record for student suspensions is going to change, according to the principal at Roger B. Taney Jr. High, Mildred Biedenkapp.

Mrs. Biedenkapp, along with the principals of the other two schools with the "in-school" suspension pilot project, studied the plan in other jurisdictions before it was implemented in Prince George's County.

"I'm delighted with the program," Mrs. Biedenkapp said in a telephone interview. She said the "alternative to suspension" would enable the county to educated students who would otherwise be "put into the street."

"We won't have youngsters loose on communities to cause additional trouble," she added.

The Prince George's County's in-school suspension plan differs from others Mrs. Biedenkapp studied. "We are going to have a maximum of three days of suspension in our detention centers, then the child's performance will be evaluated. In other systems, students can be suspended up to 10 days without evaluation." Mrs. Biedenkapp also said the use of teachers and aides will give the county program another advantage over other suspension programs she has studied.