The virginia NAACP has asked the U.S. Department of Health, Education and Welfare to investigate reports that some students were urged to stay at home on the days that state competency tests were being administered.

Jack Gravely, executive secretary of the civil rights group, said during a state education conference here that he has urged HEW officials to check how the tests were run in three counties. He did not name the counties.

Mrs. Paul H. Coussens, president of the Virginia Congress of Parents and Teachers and another panelist at the education meeting, said she also had heard reports that students who where doing poorly were told to stay at home when the tests were being given.

The competency tests were given to 10th graders in the fall of 1978 and to ninth graders last spring. The Virginia NAACP has expressed displeasure at results that showed blacks did worse than whites on the tests.

The panel members here expressed mixed opinions of the competency tests, which are required for high school diplomas, but all agreed the test itself should receive extensive study.

"The jury is still out on the competency tests," Gravely said. He said testing will mean little if Virginia's educational system is not improved.

Gravely said he was concerned about the impact of the competency tests on a student's future. "One test must not be the yardstick to evaluate a student for the rest of his life," the NAACP secretary said.

Gravely also called for earlier compretency-type testing, so academic deficiencies can be detected.

S. John Davis, the state's new superintendent of public instruction, told the conference in an opening addrress that he, also, wants to see competency-type testing begun earlier.

Schools need to know in what areas students and teachers are deficient, he said, so additional instruction or training can be provied.