The Fairfax County School Board approved a plan last night to restructure the way it educates the county's 30,000 sixth-, seventh- and eighth-graders in an effort to ease their transition into adolescence.

Under the program, middle school classes will be less tied to the rigid high-school-style bell schedules, allowing teams of teachers far more flexibility in arranging their lessons. This concept, popular for decades in other parts of the country, has spread recently through the Washington area.

School officials said the reconfigured class structure is intended to move children more easily from the nurturing environment of elementary schools to the high-pressure atmosphere of high schools. Student School Board member Timothy B. Nee, a senior at W.T. Woodson High School, said current middle school students often feel "left hanging there in the breeze."

"I really wish this were around when I was going through junior high school," he said.

In the works for three years, the plan was approved with just one abstention and has been met with widespread support from teachers, principals and parents.

However, difficult questions remain. The so-called middle school philosophy generally prefers that sixth-, seventh- and eighth-graders be educated together in the same building. In Fairfax, though, sixth-graders attend elementary schools while seventh- and eighth-graders are grouped in intermediate schools.

Beginning in September, three of the county's 23 intermediate schools will be converted into middle schools by adding sixth-graders, but there could be enormous cost and facility problems involved in making such a change countywide. Moreover, the idea of mixing 11-year-olds with older students remains unpopular among some parents.

The board directed its staff to study the effect of adding sixth-graders to the remaining 20 intermediate schools and to evaluate the newly reorganized Poe, Holmes and Glasgow middle schools by August 1992.

The instructional changes approved last night will group students in clusters with four teachers in adjacent classrooms. Instead of rigidly following the 47-minute class schedule, they may spend two hours in one class on some days and then none in that class the following day.

Advocates said the greater flexibility will allow teachers to plan joint lessons and spot students' troubles more quickly because they will all share the same children.

"This will give them a sense of a small family grouping within a large school," said Linda Whitfield, head of the Fairfax County Intermediate Principals Association.

In other action last night:

Armando M. Rodriguez, the first Hispanic person to serve on the board and the Mount Vernon District representative since 1988, announced that he will retire on June 1.

The board named the new school scheduled to open in Centreville this fall the Ormond Stone Intermediate School in honor of a prominent community leader.

School Board Chairman Kohann H. Whitney set a May 14 public hearing to receive testimony on how the School Board should deal with nearly $30 million in school budget cuts ordered this week by the Board of Supervisors.