Hundreds of District of Columbia public school students will find that they have no classroom teacher when they arrive for the opening of school today.

The unexpected retirement of 175 teachers in the last week has forced school officials to assign parents, non-professional educational aides who often do not have any college education, special reading and math instructors and school counselors to the teacherless classrooms.

City school personnel officials said they expect that every classroom will have a regular teacher by Monday, and possibly by tomorrow. But for the opening day, some schools will be short from one to six teachers, a spot check of schools showed.

The shortage of teachers is partly a result of the unprecedented layoff of 740 teachers this year, a measure designed to help solve the city's financial crisis. But after city officials had reassigned hundreds of teachers to ensure that each school had a sufficient number, another 175 teachers with at least 20 years' experience took advantage of a special offer from the school system to retire with losing a significant amount of their pension benefits.

The special retirement plan did not take effect until last Saturday, and the teachers did not start to retire until this week. As a result, school officials then had to start rehiring and reassigning some teachers who had been laid off.

School Suuperintendent Vincent E. Reed said the personnel department worked through last night calling teachers who previously had been laid off and directing them to report to work.

He said that each year some schools run short of teachers at the beginning of the school year. But he said, "We've never gone through such a massive shake-up, switching around and reassigning, as we have this year . . . Hopefully, we will have everything in order by Monday."

School officials said they did not know exactly how many schools are still short of teachers. A spot check of 15 elementary schools yesterday showed that 10 of them are lacking some teachers.

"I think in almost any elementary school you go in, you will find insufficient staff, meaning there will be classrooms not covered. In other schools, you will find they've doubled classrooms, put two classes on one teacher," said Harold Fisher, assistant teacher," said Harold Fisher, assistant to the president of the Washington Teachers Union.

Larry Paige, of the Friendship Educational Center on South Capitol Street, said the late assignment of teachers has made it difficult for principals to plan their school year.

"Teachers, by the time they come on board, will not have had the chance to talk to me about what they want to do with the kids this year," Paige said.

In addition, Paige said, there was virtually no chance for principals this year to request the transfer of teachers that they did not think would work out at their schools.

Because of the massive layoffs, many teachers will not be returning to the schools where they taught last year. Teachers who have taught a certain grade level for many years will suddenly find themselves teaching a new grade. Principals say the reshuffling has not only been a source of consternation for themselves and for the teachers, but for the parents as well.

Key School on McArthur Boulevard NW, for example, lost one of its most popular teachers who consistently succeeded in raising the reading levels of her students, according to principal Betty Brooks. Brooks said the teacher, Jeanne Bridgett, was laid off because she was classified as a temporary teacher.

"It's difficult for the children and for the parents to understand why she's not returning," Brooks said.

At Key, which has five grades, three of the six teachers will be new ones.

"Parents are panicking. They know they had good teachers at Key last year, but they don't know how the new ones will be. Some of the double registering their kids at Key and at a private school, just in case," said Karen Ferguson, a parent of a Key student.

All through the summer, principals have been forced to perform a delicate juggling act to decide what programs will have to be cut in order to keep within their shrinking budgets.

Brooks, who is principal of both Hyde and Key Elementary Schools, said she had to sacrifice having a special math and reading teacher for both schools in order to hire one more classroom teacher for Hyde.

Terrell Elementary School on Wheeler Road SE will have no art or foreign language instruction this year.

Murch Elementary School, on 36th and Ellicott streets NW, has had to cut back its special science resource program from five days to three.

Several elementary schools will also have more crowded classrooms as a result of the teacher layoffs. Although school officials said the official pupil-teacher ratio in the elementary grades should be 28 to 1, principals say as many as 31 students will be in each class year.