When Paul Junior High School in Northwest Washington needed a mathematics teacher last fall, a business teacher was drafted for the general math classes, Iona Brown told a Senate committee yesterday. When the school lost a science teacher, she said, a physical education instructor who had taken a few science courses was told to fill in.

"I'm afraid teachers are assigned very often to math or science because they can add and subtract, and multiply and divide," said Brown, a mathematics teacher at Paul, "and I don't think that's unique to my school."

Yesterday Brown and six other teachers from the Washington area gave a front-line view of science and math education to the Senate Labor and Human Resources Committee. The committee chairman, Sen. Orrin Hatch (R--Utah), declared that "math and science education has been woefully neglected" in the public schools, and said his panel is considering several bills to upgrade it.

The teachers had warm words for their students and subject matter, but most said a lot of upgrading is needed.

"I know many teachers who can't do anything more in science except follow the book," said Regina Mitchell, a fifth-grade teacher at Rock Creek Forest Elementary School in Montgomery County. "If they start an experiment and it doesn't work, that's the end of science for the year."

Mitchell said she liked the county's new science and math curricula, but even these have problems: too much paper work and not enough teaching materials. It is also difficult to teach science to large classes, she said.

"I can teach language and social studies before a class of 34," Mitchell said. "But if you are going to make science more than a vocabulary list, you have to have time for experiments . You need an opportunity to solve problems . . . . We don't have much of that."

Clinton Brown, chairman of the science department at Richard Montgomery High School in Rockville, said the National Science Foundation developed "very good" curricula in physics, biology and chemistry around 1970. But most of these are "on the shelf," Brown said, because the programs don't prepare students to do well on the college board achievement exams.

"We're encouraged to teach to the college entrance exams," Brown said, "and these ask for much more factual material and memorization than the inquiry and discovery method was giving them."

In March, the House passed a $425 million bill to improve math and science education. It would buy new equipment and provide training to update the skills of science teachers, offer retraining to teachers of other subjects and provide scholarships to college students who promise to become math and science teachers.

The Reagan administration has proposed a $75 million program aimed at training science teachers and offering prizes to the best ones. Sen. Claiborne Pell (D-R.I.) has offered a more expansive bill, and Hatch is preparing a bill of his own.

Yesterday, Louis Goffredi, chairman of the mathematics department at Wakefield High School in Arlington, said any money in the bills for teachers to take courses in the summer would be welcome. "I want to keep up with the new material," Goffredi said, "but during the summer I can't afford to. I have to take a job. I have a family and a mortgage."

But Clinton Brown said unless training is tied to higher teacher salaries, it is not likely to accomplish much.

"I've seen four excellent teachers leave for industry," Brown said. "Their replacements were not trained in science , and they are now being trained. But once they have the training, I'm afraid there'll be no stopping them in going for the higher salaries in business."