The Washington school system has found new jobs for 38 of the 70 tenured teachers who received layoff notices last week, but the programs in which the teachers participated, including elementary school foreign languages, remain severely curtailed.

Claudette Helms, the system's personnel director, said the new jobs became available because other teachers quit or took leaves of absence.

"I hope by the end of the month we will be able to place all of (the fired teachers)," Helms said, "but we just don't know. And even if we solve the problem for this year, it only means we've delayed it until next year.

"We're kind of playing checkers," she added, "and it gets kind of sticky."

Yesterday was the first day of the fall term for an estimated 122,500 students in the city public schools. About 2,000 of them attended classes for the first time in two large new buildings - Shaw Junior High School, at Rhode Island Avenue and 10th Street NW, and Reed Elementary (formerly Morgan) at 18th and California Streets NW.

Both schools were completed several years behind schedule and their enrollment is substantially below capacity, but most of the students who came to them yesterday seemed enthusiastic.

"The school's just big and pretty, and has all different colors," said Deseree Holliday, a fourth-grader at Reed, "and the bathrooms are pretty too."

Both Shaw and Reed have large carpeted classrooms, holding several hundred students apiece. They also have Olympic-size indoor swimming pools, and model apartments for "family living" courses that include kitchen appliances and modern furniture. At Reed there is a large fireplace decorated with a picture of Bishop Marie community board, after whom the school was named.

The two new schools also have large health suites, day-care centers, and rooms for community activities. The city government has not appropriated enough money to run programs in them. As a result, the community rooms at Reed were locked and empty yesterday. At Shaw some of them are being used for administrative offices.

"I hope we'll have something in these rooms soon," said John H. Anthony, the principal at Reed, "but we just don't know. Money is a problem."

At the heart of the school system's money problems is its declining enrollment - down an estimated 3,500 from a year ago, about 27,000 less than its peak seven years.

Although the school budget continues to increase because of higher salaries and pensions, the city government has cut the number of teachers who can be employed this fall roughly in line with the drop in enrollment.

Supt. Vincent E. Reed said most of the cutback of about 240 teaching jobs was achieved through retirement and resignations. He said the 70 teachers were fired in fields where local school principals and parents did not want their services.

Among those laid off were 19 of the 32 teachers of Spanish, French, and Latin in elementary schools, 16 of the 70 elementary music teachers; 10 teachers in elementary art, seven in physical education, and lesser numbers in home economics, shop, and business. At least two of the fired teachers had 17 years' experience.

Yesterday Mrs. Helms said she did not know in which fields teachers had been rehired, but she emphasized that they could only come back to teach the same subject they taught last year if another teacher in that subject had quit. Otherwise, she said, the laid off teachers might get jobs in other positions for which they have propert credentials. In each case, she said, rehiring depends on seniority in the field in which an opening occurs.

Josette Schrader, a French teacher laid off with 16 years experience, said she was still waiting to hear if she had a new job yesterday.

"It's kind of hard to look for anything in the fall," she said, "or even to enroll in courses. I'm just sitting tight."

Meanwhile, in the schools themselves opening day seemed to go smoothly. Among the students returning to class was President Carter's daughter Amy, now a fifth-grader at Stevens Elementary School.

Although the D.C. school system is losing students overall, principal Lydia Williams said the enrollment at Stevens, 21st and K Streets NW, is up about 10 per cent compared to a year ago.

The new students include the childnre of two White House staff members she said, and the son of the ambassador of Zambia.