DENVER – The video shows a fourth-grade music teacher leading her pupils through four-beat patterns with a rest. Two dozen judges are watching, grading how well she’s engaging students and leading the lesson.

None of the judges is a music teacher. They’re school administrators learning how to evaluate educators in a discipline not their own. It’s no easy task, and as Colorado prepares for statewide implementation of standardized educator-effectiveness ratings, it’s the kind of thing many schools are going to be doing in every classroom.

Colorado adopted a statewide teacher-grading system three years ago, a rating that sorts educators from “highly effective” to “ineffective.” Teachers with too many consecutive low ratings could lose tenure, while new teachers and those on probationary status will need passing marks before achieving tenure, or nonprobationary status.

After three years of development and pilot tests, the effectiveness ratings will begin for all 178 Colorado school districts this fall. The stakes are high, and many teachers in Colorado aren’t exactly sure how it will work.

“There’s massive anxiety about it,” said Stephanie Rossi, a social studies teacher at Wheat Ridge High School in Jefferson County, the state’s largest school district. “Are we ready for it? No, because we don’t know what it is.”

The teacher and administrator ratings will be 50 percent based on student test scores. The rest of the rating is based on more subjective evaluations of how well teachers perform.

Denver is training administrators and teachers in peer evaluations, where teachers will be graded on everything from how they use technology in their lessons to how they respond to pupils who don’t understand certain instructions or terminology. Student feedback is also a factor, with children getting to weigh in on how their teachers are doing.

The teacher evaluators were training recently about how to make sure they arrive at similar ratings, even in a subject area they’ve never taught. The evaluators reviewed guidelines after seeing the music video, then raised fingers to show how they would have rated the example lesson.

“What did you guys get? Fours? Fives? OK, let’s look at the exact evidence,” said Danielle Ongart, who is leading the training for Denver Public Schools.

The administrators reviewed the lesson. Did students learn the pattern or just mimic the teacher? How did the teacher monitor student progress? Was the lesson adjusted based on how the pupils responded? The evaluators went through pages of detailed benchmarks to decide a final rating.

The goal of the exercise was to make sure observations result in similar scores for the teachers, regardless of who is observing them.

Denver Public Schools started rating all teachers last year, but the ratings don’t start counting toward tenure until this school year.

By the 2014-15 school year, the ratings can start damaging teachers rated “ineffective.” Teachers with tenure face losing that status after two years of “ineffective” ratings. Struggling teachers are supposed to receive extra help to improve student outcomes.

State education officials say they’re helping smaller districts adjust to the new teacher rating scheme. But resources are scarce, and schools are still climbing back to budget levels they had before the recession.