Three-year-old Johnny Bigley, the Anne Arundel County boy whose case of herpes has caused the exodus of his preschool classmates, could be barred from school as many as 45 days a year if officials adopted guidelines sought by teachers and parents of other children at his school, his parents said today.

However, in a hearing before the county Board of Education, attorneys for teachers and parents seeking more stringent conditions for the child's enrollment argued that Johnny would probably miss much less school than that under the restrictions they propose.

They are asking the school board to overturn a decision by Superintendent Robert C. Rice allowing the boy to attend school unless he has active lesions on his hands or face. Under Rice's guidelines, Johnny would be allowed into class at Pasadena Elementary School when he has lesions elsewhere on his body that would be covered with clothing or bandages. The teachers and parents of five children who would be in Johnny's class are asking school authorities to prohibit the boy from attending school when he has any active herpes sores.

An attorney for the teachers and parents, Susan Russell, told the board today, "It is only common prudence to not allow this child to be in school while in the active stage of his disease. We're not asking that he be kept out totally."

The board heard more than five hours of testimony today in the continuing, emotional controversy and said it would probably make a decision by its next meeting, scheduled for Feb. 6.

Herpes is a viral disease that commonly results in lesions or blisters on the skin. The boy contracted the disease shortly after birth. It is unknown whether he has the common variety that causes cold sores or another type known as genital herpes.

Edward Bigley said his son had active lesions eight or nine times last year, lasting from three to five days each. Russell argued, however, that because of medication and the fact that some outbreaks may overlap or occur on weekends, "it might be very little time" that the boy misses from school.

None of the five other children in the class has attended school since the boy began school three weeks ago as part of a special class for children who are developmentally behind their age. Under federal law, Johnny is entitled to receive some instruction even at his age because of his disability, which is primarily a speech problem. That problem is not related to the herpes.

Attorney P. Tyson Bennett, who defended Rice's decision to allow the boy to attend school, responded that "adequate and sufficient" safeguards have been ordered.

Mary Madeleine, director of special education for the school system, said, "We were assured by everybody we talked to . . . there is no reason to keep him out of school if those lesions were covered. I don't think we have to treat him like a leper."

Jane Timberg, who previously taught Johnny's class, requested and was granted a transfer to another school because she suffers from a skin condition that makes her susceptible to infection, she said.

"I hated to leave that class," she said. "I feel very sorry for Johnny. I feel very sorry for the kids in the class.