Teachers and principals in the Prince George's County school system will get a series of pay raises under two-year contracts approved last night by the school board.

The agreements with the teachers and principals unions guarantee 2 percent raises retroactive to July 1, followed by 1 percent in January. The employees will get an additional 3 percent in the second year of their contracts.

Carol Kilby, president of the Prince George's County Educators Association, which represents about 9,000 teachers, said the group's membership supported the agreement because "it's a two-year contract . . . that gives us time to breathe."

Howard Burnett, the school system's chief administrator for human resources, agreed. The multiyear contracts, he said, "help us both retain and recruit quality employees throughout the school system."

Under the new contract, the starting salary for a Prince George's teacher with a bachelor's degree increased from $36,101 to $37,910. The average salary for a teacher with a bachelor's degree is now $48,440, according to the school system.

The school board also ratified contracts last night with unions representing bus drivers and custodians.

In recent years, negotiations have been tense and prolonged between the school system and its unions, whose members have been working under terms of contracts that expired in July.

Doris Reed, executive director of the Association of Supervisory and Administrative School Personnel, the union representing about 620 principals and other administrators, said principals in the county continue to be paid less than their counterparts in neighboring school systems. Reed did not provide salary figures for such a comparison last night.

Some Prince George's unions negotiated concessions beyond salary. Elementary school teachers, for example, will be allowed to spend 350 minutes each week planning for their courses, instead of the current 225 minutes. Also, the teachers no longer will have to monitor cafeteria and recess time; the school system plans to hire aides to take over those duties, Kilby said.