Fairfax County school officials announced plans for a new evaluation system Monday that would base 40 percent of a teacher's performance on student achievement.

But employees of Virginia's largest school system were vocal that they had reached that decision only because the county's hands were tied by decisions made by the state and federal governments: The U.S. Department of Education refused to approve Virginia's application for relief from No Child Left Behind unless the state agreed to make the 40-percent share mandatory.

"We don't have an official memo from [state Superintendent] Pat Wright saying it must be 40 percent, but they did put out this press release ... ," said Richard Moniuszko, deputy superintendent of Fairfax County Public Schools.

Steven Greenburg, president of the Fairfax County Federation of Teachers, said he was "absolutely disgusted that the U.S. Department of Education would leverage" the evaluations so Virginia's application could be accepted.

Officials spoke of political and public interest in teacher evaluation systems that link students' achievement -- often judged by test scores -- and teachers' performance. Much of that interest began in the District, where standardized test scores comprise up to 50 percent of teachers' evaluations and where hundreds of teachers are fired each summer when the evaluations are released.

Fairfax County's solution to the state's mandate is a far cry from the District's method, described as "a little Draconian" by Denny Berry, the director of schools that feed into West Springfield High School and Robinson and Lake Braddock secondary schools. She also is a leader of the evaluation task force.

To measure student progress, each teacher would set goals that do not need to be based on Virginia Standards of Learning test scores. Instead, teachers can set goals based on performance -- or even enrollment -- in Advanced Placement or International Baccalaureate courses, among other measures.

For example, a fourth-grade reading teacher could set a goal to have all of his students at or above grade level, as determined by the county's Developmental Reading Assessment.

Teachers would be rated "highly effective," "effective," "needs improvement/developing" or "ineffective" in that and six other categories.

Berry said the county has yet to decide how the new ratings would translate to teacher terminations; for instance, she does not know what would happen to a teacher rated "ineffective" in one of the seven categories.

Virginia is requiring its school districts to create the new systems by July 1. Officials said they will have the system ready for the new school year.