Three members of the Fairfax County School Board who are to attend a national convention in San Francisco this month have decided to give up their reservations at the five-star Stanford Court, where rooms cost $127 to $187 a night, in favor of more economical digs.

Their decision to move to the Stewart Hotel, four blocks down the hill from the prestigious Nob Hill address of the Stanford Court, means they will pay at least $50 a night less since rooms there will cost $50 to $75.

The decision of at-large member Robert E. Frye, Dranesville's Mary E. Collier, and James W. Kitchin of Mason, means that, of the Northern Virginia convention representatives, only those from Arlington and Alexandria will be staying at the Stanford Court or the city's only other five-star hotel, the Four Seasons-Cliff.

Arlington Board Chairman Evelyn Reid Syphax and Superintendent Charles E. Nunley have retained their reservations at the Stanford Court. The Alexandria delegation, which includes three board members and Superintendent Robert W. Peebles, has booked rooms at the Four Seasons-Cliff, which will cost between $90 and $155.

"It's a valiant thing for the Fairfax County representatives to do on their part," said an amused Marilyn Rogers, president of the Fairfax Education Association yesterday. "It's only fair and just that they show some fiscal restraint." Both the FEA and the Fairfax County Federation of Teachers had called for the representatives to move to a less expensive hotel.

The Stewart Hotel, which an assistant manager described as "economy, definitely," is "right behind" the Hilton, center of activities at the April 22-26 convention. While the Stewart cannot match the luxuries of the Stanford Court it offers remote-control televisions with pay movies.

"I had a travel agent from Texas call me to make reservations for some school board people from her area , and she was really put out," said a Stanford Court reservations clerk. "She said, 'It's great for me, because I make a commission, but it's my tax money they're spending!' "