Increases this year in the cost of optional summer-school courses offered by some Northern Virginia public school systems have forced many parents to forgo summer school for their children, officials say.

Particularly hard hit are those families, many of whom are immigrants or refugees, who want their children to continue special English classes, officials say.

"There are a large number of students who are unable to attend summer school because they can't afford it," said Emma deHainer, who oversees those Arlington programs that provide intensive language training for students whose native language is not English.

DeHainer said an informal poll of students in those programs in intermediate and senior high school found 50 percent of them could not afford to continue with the summer language courses, which cost $90 to $110 a student. According to deHainer, those fees are multiplied in some families with one or more students seeking the courses. "Many of the students are from large families," deHainer said.

In a poll of families of elementary school students in those programs, deHainer said, "the story was the same."

About 15,000 Fairfax, Arlington and Alexandria students are expected to enroll in summer school this year. But what used to be for many a regular routine has now, for some, become a barely affordable luxury.

School systems in Northern Virginia now charge tuition for summer learning--sometimes up to $200 a course. And this year, some school systems faced with economic belt-tightening during the regular school term are increasing tuition and tightening the requirements for getting certain fees waived in an effort to keep their costs low.

Although the schools may waive or reduce fees and tuition increases are generally only slight, the costs are still a problem for many families, according to Arlington parent and teacher groups that have been organizing spring fund-raising events to pay summer school tuition for needy students.

Perhaps more than most students wishing to attend summer school, those students taught English in special programs want to continue their schooling during the summer because they see it as vital to their success in American schools.

Language skills learned during the regular school year can be lost during the summer by children whose parents speak little English or those who live in households where only the native language is spoken.

Tests showed, for instance, that the English skills of 64 percent of the students were lower last fall than they were in the previous spring, deHainer said. "They regressed in their English aquisition."

To defray summer school costs for some students, a Latin American parent's group in Arlington recently raffled an imported handmade tablecloth and napkin set and raised more than $200, while a Vietnamese parents groups raised summer school scholarship money at a community dinner.

Meanwhile, teachers at Glencarlyn Elementary School raised more than $2,000 after holding a variety of events. That money is to be used to pay summer school costs for some English language students as well as other students because, as deHainer puts it, "All low-income kids need it."

In Arlington, summer school tuition is up 6 percent from last year, ranging from $28 for a 10-day art class to $180 for a 32-day academic course. The system has budgeted $44,000 this year for costs not covered by the tuition of an estimated 3,000 students who are expected to spend much of their summer in classrooms.

Costs are up in Fairfax and Alexandria as well, where students will be charged from $50 to learn how to play the violin to $120 to learn about astrology, archeology or the environment.

Last year, Alexandria offered, at no cost, only remedial courses. This year, city schools, expecting 2,300 pupils, also will offer enrichment courses, including computer literacy for an average of $50 a course. The remedial courses again will be offered free, Alexandria schools spokesman said Mel Alba.

In Fairfax, school officials expect to spend $2.7 million administering a summer program for 10,000 students. The School Board has been moving to make the summer program more self-supportive, instructional services director Max Skidmore said.

In Alexandria and Arlington, individual determinations by school principals are usually enough to waive or reduce a needy student's summer-school tuition.

Fairfax officials are relying less on the recommendations of principals and more on a formula that bases waivers on whether a student qualifies for free or reduced-price lunches during the school year. This year, students qualified for reduced-price lunches may have one-half of the tuition waived. Up to two-thirds of the tuition may be waived for students eligible for free lunches. In cases of dire need, all but $5 could be waived, Skidmore said.

In all schools, fees for nonresidents are significantly higher than for residents, and remedial courses generally cost less than enrichment courses.