A proposal to establish a separate high school diploma for Virginia students who complete a college preparatory course of study is under attack by state education groups, which call it elitist.

The proposal is one of several recommendations by a 17-member committee on public school accreditation and is scheduled to go before the state Board of Education when it meets Jan. 20 and 21, said committee member John Foley, a state supervisor of accreditation.

Other recommendations include increasing the minimum number of credits needed for high school graduation from 18 to 20 and requiring high school students to remain in school the entire academic day, said Foley. State regulations now allow high school seniors to leave school premises when they finish their last class of the day, though many school districts have their own policies prohibiting this.

The committee recommends that the college preparatory diploma be awarded to students who earn 22 credits, including three credits each in mathematics, science and a foreign language, said state Supervisor of Accreditation Robert Jewell. A credit is awarded for one year of study.

"It will prepare those students who are heading toward higher education," said state Superintendent of Schools S. John Davis. "Colleges have been complaining that our students are unprepared."

Some state educators, especially those in vocational education, argue that the special diploma will devalue the general diploma earned by other students. The Virginia Vocational Association and the State Association of Professional Vocational Educators have adopted resolutions condemning the proposal.

"This diploma is an elitist status symbol and it doesn't do anything anyway, because the high school grades transcript is what colleges look at," said George Orr, executive director of the state's vocational education advisory board. "It will only serve to separate and categorize our students and create tension between them."

Orr is a member of the accreditation committee appointed by the governor last spring.

Some other states have adopted the college preparatory diploma in the wake of accusations that their students are unprepared for college, Davis said. Public universities in Ohio, one of the first states to adopt the idea, are required to admit students with college prep diplomas. New York offers special recognition to students passing a rigorous exam. The District of Columbia and Maryland do not have separate college preparatory diplomas and have no immediate plans to create them, officials said.

The committee proposal to make students stay in school all day also is controversial because many students leave for after-school jobs. Davis said students working as part of a study course will not be affected by the recommendation and that those with financial hardship may receive permission from their local superintendent to leave school early for jobs.

The recommendations will be the subject of public hearings this spring, Jewell said. If adopted, they would take effect in the fall of 1984.