A sum of $46,000 disbursed by the Montgomery County school system has triggered angry charges of favoritism by the county's teachers union but pleasantly surprised the 46 school administrators who each received $1,000 bonuses.

The bonuses were authorized by former school superintendent Edward Andrews for "exceptional performance" and were designed to reward such officials as George W. Fisher, who often labored many hours beyond their regular workday without extra pay.

As the facilities planning director for Montgomery schools, Fisher spent many a night and weekend last fall drafting a voluminous 15-year plan on the county's 150 school buildings currently in use.

He and the other administrators received their bonuses in June, a move that angered some teachers who oppose the concept of merit pay in general and the use of such bonuses in Montgomery.

"It's always nice to get your work recognized," said Fisher, "when that work is done well or satisfactorily."

Others, however, contended that even a well-intentioned system of bonuses--rewarding employes for jobs well done--cannot be administered fairly. "This system leads to all kinds of favoritism," said Jean Stern, president of the 4,700-member Montgomery County Education Association. "There was no concrete criteria used to decide who would get bonuses. People were awarded based on who they knew, not on what they knew."

Thirty-seven administrators received the awards under provisions of the 1982 contract between the school board and the Montgomery County Association of Administrative and Supervisory Personnel (MCAASP), the union that represents 348 top school officials. The 37 were nominated for the award by the county's seven associate superintendents; the nominations were reviewed and later approved by Andrews.

The nine other bonus recipients, including Fisher and others who were not MCAASP members, were recommended solely by Andrews, said school department spokesman Kenneth K. Muir, himself a bonus recipient.

"They did not give the bonuses to the 46 best administrators in the county," said Stern, whose union has rejected a bonus clause in past contract negotiations. "The bonuses were given to the most visible administrators, members of a tight little group in the central office.

"Taxpayers' dollars were used . . . to reward Andrews' friends," Stern said.

Not so, Muir said. "Certainly many of the 46 work or have worked in the central office," said Muir, whose after-tax bonus amounted to $670. "But in every case the bonus was awarded for work above and beyond the call of duty."

MCAASP President Catherine Derby said that although the cash awards were a "worthwhile" incentive and reward, school officials should consider alternatives to the bonus system.

"Other incentives, such as sabbaticals, or special one- or two-month projects could be explored," said Derby, principal of Travilah Elementary School in Gaithersburg. "There are other things besides money that could be used as rewards."

School Superintendent Wilmer S. Cody, who inherited the bonus system when he replaced Andrews earlier this year and who is expected to approve two future rounds of annual bonuses, said he might consider alternatives to the cash awards.

"That's not to say that the ones who received the awards didn't merit them," Cody said. "They certainly did that."