More District of Columbia students will attend summer school this year than ever before because new academic standards are forcing athletes and other students to take remedial classes, and special programs are attracting youths willing to give up their vacation time, city school officials said yesterday.

Summer school started in Washington yesterday with an expected enrollment of 16,000 students, which is an increase of 2,000 over last summer, said Barbara Jackson, D.C. schools assistant superintendent and coordinator of summer school.

According to the projected enrollment figures, about 18 percent of the total student population is expected to attend the six-week summer school session.

By comparison, 8 percent of Fairfax County students and about 6 percent of Prince George's County students will attend summer school, according to figures supplied by county school officials.

Current figures were not available for Montgomery County, but last year about 20 percent of students attended summer school, with many attending enrichment programs.

The increase in summer school enrollment, Jackson said, is due in large part to the recent school board decision to require students involved in sports and other extracurricular activities to maintain a C-average to remain eligible to participate in those programs. That policy takes effect in the fall.

Jackson also pointed to programs instituted within the last two years that require seventh and eighth graders to pass rigid requirements on citywide academic tests. The tests, part of the Secondary Student Progress Plan SSPP , were implemented for eighth graders last year and went into effect for seventh graders in the 1984-85 school year.

About 30 percent of all seventh graders last year failed English, math, science or social studies courses, and school officials are expecting large numbers of seventh graders as well as eighth graders to attend summer school.

School officials said specific enrollment breakdowns will not be available until next week.

Jackson said that teachers and principals spent a lot of time last year encouraging students with academic deficiencies to attend summer classes.

"We have the C-average ruling and we also have instituted the SSPP in grade eight and we have a number of students involved in summer classes to meet these new requirements," Jackson said of the increased summer school enrollment.

"We also have expanded courses for exceptional students and severely handicapped students, as well as bilingual students who need remedial help in English," she said.

"We are feeling that we are going to have one of the finest summer programs we've ever had because we're addressing a number of needs within the school system. We're providing opportunities for our students to be better prepared in the fall and to do some creative things they'd like to do," Jackson said.

Summer classes are being offered at more than 50 D.C. schools, where about 860 teachers and administrators will supervise students from 9 a.m. to about 12:30 p.m. Monday through Friday until Aug. 7.

In addition, evening courses are offered for adult students, Jackson said.

In an unrelated matter, the D.C. school board voted yesterday to approve a plan to consolidate several Capitol Hill schools under a pilot program designed to both enhance the academic growth of students as they progress from kindergarten to eighth grade and also induce more parents to keep their children in public schools.

Staff writer Lisa Leff contributed to this report.