But seven years of student test scores suggest otherwise.
In the Times analysis, Caruso, who teaches third grade, ranked among the bottom 10% of elementary school teachers in boosting students' test scores. On average, her students started the year at a high level — above the 80th percentile — but by the end had sunk 11 percentile points in math and 5 points in English.
Caruso said she was surprised and disappointed by her results, adding that her students did well on periodic assessments and that parents seemed well-satisfied.
"Ms. Caruso was an amazing teacher," said Rita Gasparetti, whose daughter was in Caruso's class a few years ago. "She really worked with Clara, socially and academically."
Still, Caruso said the numbers were important and, like several other teachers interviewed, wondered why she hadn't been shown such data before by anyone in the district.
"For better or worse," she said, "testing and teacher effectiveness are going to be linked.… If my student test scores show I'm an ineffective teacher, I'd like to know what contributes to it. What do I need to do to bring my average up?"
During recent classes observed by a reporter, Caruso set clear expectations for her students but seemed reluctant to challenge them. In reviewing new vocabulary, for instance, Caruso asked her third-graders to find the sentence where the word "route" appeared in a story.
"Copy it just like it's written," she instructed the class, most of whom started the year advanced for their grade.
"Some teachers have kids use new words in their own sentences," Caruso explained. "I think that's too difficult."
She dismissed the weekly vocabulary quizzes that other teachers give as "old school."
Down the hall from Caruso, fourth-grade teacher Nancy Polacheck was grilling her students on vocabulary, urging them to think hard about what the words meant.
"Don't be a robot!" she said.
Polacheck is another teacher whom Oh identified as one of her top performers. And the Times analysis suggests that the principal is right: Polacheck's students gained 5 percentile points in math after a year in her class, and 4 points in English. That put her in the top 5% of elementary school teachers.
An animated woman with a blond ponytail flowing from the top of her head into her bespectacled eyes, Polacheck has been teaching for 38 years. The desks in her classroom are often set up like seats around a stage, with Polacheck, a self-described "drama queen," in the center.
Her teaching style is a rat-a-tat-tat of questions, the most common of which is "why?"
Polacheck said her colleagues at Third Street think her expectations are too high. She was reluctant to be singled out in any way, repeatedly asking a reporter why she was being interviewed.
"In the past, if I were recognized, I would become an outcast," said Polacheck, who eats her lunch alone in her classroom. "They'd say, 'She's trying to show off.' "
A long process
As the district was appointing the task force and seeking federal dollars, some enterprising principals in L.A. schools began making back-of-the-envelope assessments of teachers using raw test scores.
One clear lesson so far: Finding the least effective teachers is only the first step in a long process.
In 2008, officials at Sunrise Elementary in Boyle Heights, one of 15 campuses under Mayor Antonio Villaraigosa's control, identified several teachers whose student scores were sliding.
The mayor's Partnership for Los Angeles Schools gave them math and literacy coaches, more feedback and the opportunity to watch their more effective peers, said Angela Bass, the group's former superintendent of instruction.
Of three Sunrise teachers who ranked in the bottom 10% districtwide, just one has dramatically improved, according to the Times analysis.
Bass acknowledged that it could take years for foundering instructors to improve, if they do at all. In the meantime, about 20 students a year will continue to sit through their classes.
"It's tragic," Bass said. "It means we've failed them."
Miko Dixon, the principal at Topeka Drive Elementary in Northridge, took a tougher approach. Upon starting the job in 2009, she said, she identified four highly ineffective teachers. One had decided, with the approval of the previous principal, to keep his second-graders as they moved to third grade, ensuring two years of poor teaching in a row.
"It's criminal," Dixon said. "If you get a bad teacher in second and third grade, you're doomed."
Dixon has begun trying to remove the four teachers, a painfully slow process in California. It's far more likely that they will feel the pressure and transfer to another school, she said.
"That's not right," Dixon said, "but it's reality."
For now, parents remain mostly in the dark.
Even the most involved mothers and fathers have little means of judging instructors other than through classroom visits and parking lot chatter. Others don't even have time for that.