Some Georgia educators have been getting an unexpected surprise in their paychecks: extra money.

The bonuses were paid to the top 10 percent of teachers, principals and assistant principals in school districts that participated in the federal “Race to the Top” grant program.

The one-time bump in pay was based on a couple measures: by observations by supervisors during the last school year and student performance on tests the prior year. The test performance was graded according to how well students performed against similarly-placed peers on the Criterion-Referenced Competency Tests (CRCT), said Matt Cardoza, spokesman for the Georgia Department of Education.

Georgia agreed to develop a merit-based pay system and to develop a way to measure “growth” on tests when it accepted the federal funding, but only those districts that opted in were affected. Georgia is rolling out teacher evaluations using growth with the new Georgia Milestones tests, which replaced the CRCTs and are part of the broader College and Career Ready Performance Index, a report card for schools.