Summer school, that once remedial desert for high schoolers who didn't make the grade during the regular year, has blossomed into a pick-your-own garden of college courses for exceptional students.

"It's an investment in my future," says 17-year-old Patricia Goggin, a Reno, Nev., high school senior who is taking two college French courses this summer at Georgetown University. "I'm gaining not only academically, but personally, socially, intellectually. In three weeks, I've learned more than I have in the first 11 years of my education."

Summer school today often means computer programming, advanced math, political science, economics and the like. Major universities all over the country have opened their summer semesters to qualified high school students--not the repeat offenders of Algebra I, but the restless minds who "can't get what they need at a high school," says Georgetown Associate Dean Gerald J. Sullivan.

"I don't know if they offer chemistry in eighth grade" at Georgetown Day School, says 12-year-old Aaron Lav of Washington, whose math and science aptitude already has brought him to the attention of a nine-state academic talent search. So Lav is spending his summer in Baltimore, copying the chalky hieroglyphics of chemistry from a board in the steep well of a Johns Hopkins lecture hall.

"It was the first thing that got me thinking about graduating from Herndon High School in three years," says Claudia Testa, who signed up for the High School Scholars program at Johns Hopkins in Baltimore the summer after eighth grade.

Testa took Algebra II, geometry and trigonometry that summer, all for credit, which allowed her to enroll in functions and analytic geometry her freshman year and college prep calculus as a sophomore. When she enters the University of Virginia this fall, she will be allowed to skip traditional freshman math.

The new allure of summer school ("My mother suggested it when I was in seventh grade but I thought it was full of, you know, degenerates," says Alisa Adamo of Potomac, now 17) is a one part packaging and one part pragmatism.

Over the past decade, the growing tendency to focus on the special needs of academically talented teenagers has paralleled the stiffening competition for college slots and scholarships. These on-campus summer prep schools allow gifted students not only to skip more basic high school requirements, but to dress up their transcripts.

"I think it will definitely help" in applying to colleges, says Goggin. "Georgetown is not only an excellent school, it's a prestigious one. Other universities see that on your record and they know you're serious about getting the best possible education."

"I want to get some idea of how demanding a college course is," says Adamo, a senior at Bethesda's Stone Ridge girls' prep who has signed up for computer programming at American University. While Adamo figures "you can get a good education almost anywhere now," getting into a good university "is a matter of my own satisfaction."

"I think the economy has something to do with" the boom in summer education, says Teresa Schwartz, director of the Hopkins program. "It's so hard to get a job, and college tuition is so expensive, there's a tendency for parents to encourage kids if they're not working to at least get some credits."

Summer school for bright or ambitious teen-agers first took root about 10 years ago at Cornell University. Sullivan says the movement by universities may have been influenced by media reports that the Soviet Union was searching out and grooming its most gifted students. This summer, an estimated 20 percent of the nation's colleges will offer some kind of enrichment program for pre-college age students. Harvard takes 800 high school seniors and rising freshmen each summer; Northwestern University in Evanston, Ill., takes 500.

Georgetown, which first opened its summer courses to high school students in 1975, has 85 students from across the country and Puerto Rico in its Summer College for High School Juniors. Another 70 students, sophomore and up, are in college prep classes, and 39 very talented 15- to 17-year-olds are enrolled in a non-credit math modeling program.

Though Sullivan says the Georgetown program is aimed at middle-class students--above the traditional financial aid level and below the very expensive and exclusive prep-school programs--summer college is costly. Summer tuition at Georgetown is $160 per credit--$960 for a six-credit course, plus dorm costs for out-of-state students. At Hopkins, courses are eight credits at $100 a credit.

Most schools offer some scholarships, and the Center for the Advancement of Academically Talented Youth, the nine-state talent search based at Hopkins, also offers summer scholarships to students at various universities.

Nearly 700 high school students have enrolled in Georgetown's forensics and debating workshops, which are noncredit but high on most colleges' list of desirable extracurricular activities.

"We don't advertise our summer programs as a method of improving or raising SAT scores, although that's often a side effect," says Sullivan, who arranges a nonstop series of arts and activities as well as academics for his high school charges.

"What we want is for the kids to go back to their own schools and do well, or take more challenging courses. We want to broaden their education."