At The Hechinger Report, Aaron Pallas wants us to meet one of the worst teachers in the New York City Public School system. Carol Abbot, a teacher of mathematics, received her Teacher Data Report, a new teacher evaluation system adopted in the district that seeks to put a number on the teacher contribution to students’ success, and found out that when it comes to the impact her teaching had on the kids’ math and English language arts tests, she did worse than 68% of all 7th grade teachers and 100% of 8th grade teachers in the city.

Since 2007, Abbot has been teaching 7th graders at the Anderson School in Manhattan, one of the schools set up to accommodate the increased academic pace of some of the city’s smartest and most gifted students. Her students performed better on their year-end assessment than 98% of their peers, and frequently study material that is several grade-levels ahead of their age. The material tested on the city’s 8th-grade ELA is typically covered in 5th or 6th grade at Anderson.

Carolyn Abbott was, in one respect, a victim of her own success. After a year in her classroom, her seventh-grade students scored at the 98th percentile of New York City students on the 2009 state test. As eighth-graders, they were predicted to score at the 97th percentile on the 2010 state test. However, their actual performance was at the 89th percentile of students across the city. That shortfall—the difference between the 97th percentile and the 89th percentile—placed Abbott near the very bottom of the 1,300 eighth-grade mathematics teachers in New York City.

It’s possible that having learned the material several years before the test, Abbot’s students didn’t have it as freshly in mind as if they’d been taught it that year. It’s also possible that, although the test results play a large role in both the teacher’s future career and the schools’ rankings, doing poorly or doing well won’t have an impact on the students themselves. By the time the test is administered, it isn’t unusual for a type of ‘senioritis’ to have set in, since the classes are almost over and most kids already know what high school they’ll be attending the following fall.

After advocates won the right to have the teacher evaluation reports published, the district’s superintendent Dennis Walcott wrote an editorial in the Daily News to remind parents that the new value-added scores presented far from a complete picture of teacher quality.

“The data is now two years old, and it would be irresponsible for anyone to use this information to render judgments about individual teachers. Teacher Data Reports were created primarily as a tool to help teachers improve, and not to be used in isolation.

These words offer scant reassurance to Abbot, who was afraid that her low TDR score will hamper her ability to get tenure despite the enthusiastic endorsement from her school’s principal. Although it was possible that her tenure process would have concluded without difficulties, she just wasn’t willing to take the risk. Starting next fall, she’s leaving one classroom and entering another – as a student. She has quit Anderson and enrolled in a PhD program in mathematics at the University of Wisconsin-Madison.