Eight of the ten largest Summer School courses, including all of the top five, are science or math classes, a dramatic shift from last summer.

Applied Math S-10. "Introduction to Computer Science," which boasts a summer enrollment of 189, is this year's most popular summer course, according to figures released by the Summer School yesterday. It was followed by Chem S-1 and Chem S-20. "Introductory Chemistry" and "Organic Chemistry," with 151 and 139 students respectively.

Two more computer courses--Applied Math S-12. "Computer Organization and Assembly Language," and Applied Math S-9. "Computing in a Business Environment"-finished fourth and fifth, with 128 and 109 students.

Last year's top course. Economics S-1500. "Financial Accounting," lost 26 students and sunk to sixth on the list this year. Others in the top ten include S-15. "Introduction to Psychology and Social Relations," Physics S-1. "Principles of Physics," Math S-1F. "Introduction to the Calculus," and Math S-Ar, "Precalculus Mathematics."

The entire English as a Foreign Language program drew 606 students this year, up from 540 a year ago, administrators said. In addition, approximately 500 students signed up for an expanded expository writing program, up from 235 last year.

"We're more or less victims of our own success." Jeremy A. Richard, director of the expository writing program, said yesterday, adding. "We have been aided by the bad economy: I've never had such a fine pool of teachers to hire from."

"The air-conditioning could be better," Richard added.

The increase in math and science enrollment--including the end of several years of decline in the size of chemistry classes--took administrators by surprise. Marshall Pihl, assistant director of the Summer School, said yesterday.

"I wish I had some theory to explain it--I guess it's my professional responsibility to come up with one," Pihl said. "I had thought math and science enrollments, especially in the pre-med courses, would be off," he added.

"The Chem S-1 enrollment has never been larger--it's reached the absolute maximum I projected as possible," Pihl said. Chem S-20 enrollments are also up dramatically from a year ago.

But some traditional pre-med courses, including Biochemistry S-100. "Biochemistry," continue to show decreased enrollments, Pihl said.

Though Pihl said the boom in computer courses would seem to indicate a new interest in business, he added that the decrease in economics enrollment might contradict that view.

Expanded enrollments have not created space problems for most courses, administrators said. "We have plenty of room to handle the new students." Penny Chaloner, instructor in Chem S-20, said yesterday.