ANNAPOLIS, FEB. 11 -- Anne Arundel County teachers will get a 9 percent pay raise each of the next three years under an agreement announced today by the school board and the county teachers union.

County Executive O. James Lighthizer, who prompted picketing and a work protest by teachers last year by refusing to accept an 8 percent pay raise they negotiated with the school board, said he supports the new and bigger proposal made this year and will pay for it. He called the agreement "the most generous long-term contract ever negotiated in the history of this county."

Lighthizer insisted he was not influenced by the protests from the teachers, who are among the lowest-paid in the Washington area, but was eager to put the fighting behind him. Since September, teachers have regularly picketed County Council meetings asking for more pay.

"The negotiations have turned into year-round, bitter, acrimonious battles and it's just productive for nobody," Lighthizer said. "I was willing to pay a higher price just to put the thing right. You get the best deal you can and run with it . . . . I view it as an opportunity to provide a very good contract and stabilize the situation."

However, Anne Arundel County Teachers Association President Susie C. Jablinske said she believes the protests persuaded Lighthizer to soften his stance. "I can't give enough credit to the teachers who picketed, made phone calls and sent letters," she said. "It's their collective efforts, I think, that brought us to where we are today."

Under the agreement, the average county teacher's salary will increase from $31,526 to $34,491 next year and reach $40,979 in 1990, the last year of the contract. The average is roughly equivalent to that earned by a teacher with a master's degree and 10 years' experience. Starting salaries will increase from the present $18,800 to $24,346 by 1990, bringing Anne Arundel teachers closer in pay to their regional counterparts.

Lighthizer said citizens should expect better performance from the county's 3,900 teachers "as a return on their investment." He said he will set up a committee of citizens to study teacher performance and recommend ways of improving it.

"Not because teaching performance is bad -- it's good, I'm sure," Lighthizer said. "But we are continually striving for excellence."

Support for the study was expressed Wednesday by Jablinske, School Superintendent Robert C. Rice, school board Vice President Joan Cadden and County Council Chairman Virginia Clagett. Each reported no objection to the principle of using merit pay to reward teachers but said the difficulty of evaluating teachers fairly remains a major obstacle to such pay.

Jablinske and Lighthizer said today that the raises will make Anne Arundel more competitive with nearby school districts in attracting and retaining good teachers and said the size of the raises compares favorably with those offered teachers working in nearby Maryland counties.

Teachers in Montgomery County are in the middle of a contract that gives them raises of 9.5 percent, 8 percent and 8 percent over three years. Teachers in Prince George's are in the middle of a contract that gave them an 8 percent raise this year and a 7 percent raise next year, while those in Howard County are in the first year of a three-year contract giving them 8 percent raises each year.

Last year Anne Arundel teachers negotiated an 8 percent, one-year wage contract with the county school board, but Lighthizer lowered the increase to 5 percent, saying the county could ill-afford to pay more. The raise was subsequently increased to 6 percent by the County Council.

Teachers staged a work-to-rule protest, refusing to work beyond normal classroom hours, in June and until contract negotiations began in September.

Jablinske said she expects teachers to ratify the contract on Feb. 23, and will ask them to call off the picketing immediately.