In a quiet corner of Forestville High School, away from the jostling crowds and the adolescent pressures that pervade the rest of the building, 100 ninth graders are at work as part of an experiment for the Prince George's County schools. They were chosen not because they are brilliant or because they have special gifts, but because they were falling through the cracks.

They are students who had attendance or discipline problems, youngsters of normal intelligence who, for complex and sometimes unknown reasons, were slipping far below their scholastic potential. In most cases, their teachers feared that these students were headed for the sad futures that typically befall high school dropouts and chronic troublemakers.

The program, introduced this year on a pilot basis in three high schools to keep students in school and help them perform at higher levels, is known as Project SUCCESS. After only six months, officials are convinced it is working, and the county Board of Education has set aside funds to double its size next year.

"These are handpicked teachers, nurturing high standards," said Forestville Principal Paul Lewis. The results, he said, are "amazing."

Attendance at the schools is up to 91 percent, compared with a county high school average of 87 percent. Suspensions are down to a dozen or fewer at each of the three schools.

Most persuasive, however, are the grades. Half of the 300 students in the program have received a C average, officials say. When report cards were released last month, 20 of the 100 students in the Forestville program were on the honor roll.

"I didn't show anybody my grades" last year, said Margo Adams, a ninth grader in the program. Last week, she sat with a group of classmates, all of them bragging about their report cards. "My mother's not used to seeing good grades," she said.

"You try getting a few As, and your mother's eyes will bug out," said Richard Brogsdale, another Project SUCCESS student.

Prince George's, like school systems around the country, has long offered programs for gifted, handicapped and learning-disabled students, and for those whose behavior cried out for punishment and attention.

But Project SUCCESS is the first program in the county to grapple with the gray area: average students who need special help to perform at an average level.

The program, also offered at Suitland High School and at Potomac High School in Oxon Hill, attempts to break down obstacles that have prevented these students from succeeding.

In each of the three schools, students in Project SUCCESS are separated from other students for classes in math, science, English and reading and social studies. They are taught in groups of 20 or fewer, compared to the countywide average of about 30 students per class. And teachers move carefully through the material, keeping exact records and adhering to a highly structured curriculum.

"It's not that we're slow," said 14-year-old Torhea Timbers. "It's just that they want to make sure we get all the information . . . . I'd rather be right here. They pay attention to you."

That atmosphere is essential, say the project's teachers, because the most common problem with these students is a lack of self-confidence.

"High schools are too big for a lot of kids. They are abandoned in there," said Jean Fentress, who works in the Forestville program.

Barbara Washington, who teaches English and reading to the Forestville students, said the size of classes in most high schools makes it impossible to work with each student. "A lot of teachers don't know their students are failing until the end of the year," she said. "I firmly believe any kid can learn. You have to let them know you care. But in order for them to learn, they can't be disruptive."

DeShanta Smith, a student in the program, said the teachers are going over skills "we should have known in seventh grade." But because classes were crowded and teachers moved too fast, many of the students stopped attending. "If you don't understand, you don't want to come to school," she said.

If the school board approves an additional $600,000 of funding this spring or summer, the program will move into four more high schools and the three existing programs would be enlarged to include 10th graders.