About 90 teachers and counselors at the National Childrens Center, a school for the severely mentally retarded, are on strike in an effort to get safer working and living conditions both for the teachers and the students. The strikers also are seeking higher pay.

"Not a week goes by that someone doesn't get hurt," said Cathy Stratton, president of the chapter of the Washington Teachers Union, which represents the striking teachers. One student at the center, which is at 6200 2nd St. NW in a quiet residential neighborhood, recently bit a teachers finger and broke it, Stratton said. Another student kicked a teacher in the ribs and still another broke a flower pot over a teacher's head.

In an incident last March, Stratton, a thin woman of medium height, tried unsuccessfully to restrain one of the students at the center, who is more than six feet tall, from jumping from a third-floor balcony.

The student, who is believed to have tried to cut class to run to a nearby shop for a hamburger, suffered a fractured leg and arm in the fall.

"If [the student] had struggled more with me on the balcony, he would have pulled me over with him," Stratton complained.

The teachers also are seeking to bring their pay more in line with that of special education teachers in the D.C. public schools. A teacher with a bachelor's degree is paid a beginning salary of $8,500. The beginning salary for a D.C. public school teacher with the same degree is $13,000. The striking teachers are seeking a beginning salary of between $10,000 and $12,000, according to Harold Fisher, a union representative.

The center is a nonprofit organization that serves about 160 students between the ages of 5 and 21. It also offers a special program for infants and a vocational program for mentally retarded adults. It has an annual budget of about $3 million, with funding coming from the federal and city governments, the state governments in Maryland and Virginia and private contributions.

Most students have attended school despite the week-old strike, according to Dr. Samuel Ornstein, the center's director. They are being supervised by secretaries, members of the custodial staff and about 23 temporary teachers. Only seven teachers and counselors on the regular staff have crossed the picket line, it was reported.