Gonzalez, the Virgil Middle School teacher who this year won a prestigious Milken award for teaching science, said his new principal carries out rigorous evaluations. But when he earned tenure in 2005, he got nearly no feedback.
Maine of North Hollywood, who now leads the school's science Olympiad team, could recall only one observation by an administrator in his first few years, "and that was a couple of minutes."
"Being quickly satisfied that no riot was in progress, he departed," Maine said in an e-mail.
Two teachers elsewhere told The Times that their evaluation forms were falsified to show an observer was present when he or she was not. Both declined to be identified for fear of retribution.
The dearth of feedback has only worsened in recent years, as budget cuts have thinned the ranks of assistant principals, who are often responsible for evaluations.
Michelle Ereckson, a third-grade teacher at 24th Street and the school's union representative, said some administrators don't even show up for scheduled evaluations.
When evaluators do show up, Ereckson said, some teachers are well-prepared because they practiced the lesson with students the day before. Evaluators don't seem to notice, she said, even when students know all the answers.
Ereckson said she had reported her concerns up the ladder, all the way to the local superintendent. "No one does anything about it," she said. "Nobody cares."
She thinks it's no accident that the school's state test scores fell last year. "If the principal doesn't know what's going on in the classroom, you can't offer support to the people who need support, you can't offer praise to the people who need praise," she said.
Michelle King, District 3 superintendent, said she investigated the matter, attending a meeting at the school in which the entire faculty aired concerns about evaluations and other issues.
"The principal was able to demonstrate to me that she was following district policy," King said.
Glenn Parness, the union representative at Berendo Middle School in Pico-Union, cited other weaknesses in the system. One probationary teacher at Berendo was chronically late, couldn't control the class and rarely planned lessons, he recalled.
But the teacher knew that a tenure review was coming up and "shaped up for six months," Parness said.
After getting permanent status, the instructor backslid into old habits and is now "pretty much the same" as before, Parness said.
Forty-four percent of L.A. Unified principals said they don't always try to remove probationary teachers who they think don't belong in the profession, according to a 2008 survey conducted for the district by the New Teachers Project, a nonprofit.
Interviews by The Times suggest several explanations: Principals are afraid they'll get someone worse; it's time-consuming to prepare and unpleasant to deliver a negative evaluation; they learned not to be picky during teacher shortages that ended years ago; or they simply can't tell who deserves a permanent job and who doesn't.
Most important, L.A. Unified officials say, is a district culture that views struggling teachers almost as "pupils" who always have the capacity to improve.
Some officials also say principals have grown gun-shy from fierce battles with permanent teachers -- who are rarely fired and even then, can spend years on the payroll as their cases wind through a byzantine appeals process, as The Times reported in May.