Pressing on, Bridger, a 23-year-old recent political science graduate from Tennessee, told students to put away their cellphones and iPods. One student demanded to know why, muttering the F-word.
For years, Locke, on the edge of Watts, has had among the state's lowest test scores and highest dropout rates. In 2004, 1,451 students enrolled as freshmen; just 261 graduated four years later. Of them, only 85 had completed the courses required to apply to a University of California or California State University school.
A year ago, Green Dot Public Schools, which runs 12 charters serving the city's urban poor, took over the school. The effort to transform Locke has been a nationally watched test of whether such a large, deeply impoverished urban high school could be transformed by a charter operator. Charter schools are publicly funded but operate beyond the direct control of school districts, exempt from many regulations and union contracts.
Locke, which holds its graduation today, remains a troubled school, and Green Dot's strategy has relied on extra funds that may not be sustainable or readily replicable.
But despite those caveats, a qualified turnaround appears to be emerging.
Students say the campus is safer and calmer. The teachers, although mostly young and inexperienced, receive praise for being devoted and effective. There are signs of academic progress. Students repeat one point over and over: Instruction is better and nearly all teachers work hard and expect them to achieve.
Byron, the student who was sharpening pencils during the test, began the year an unmotivated senior and a Green Dot skeptic. "I thought Green Dot was going to be gone after the first month," Byron said. "I didn't think they were going to change anything."
In September, Bridger had to explain the difference between a noun and a verb. She's now well past those preliminaries.
"What kind of person does Lady MacBeth want her husband to be?" she asked her class a few days after the test.
"A murderer," said Deon, appearing more focused that day.
"What does Lady Macbeth want her husband to seem to be?" Bridger continued.
"A hero, a leader," said Daniel, who was awake that day. He works 35 hours a week at Subway, for $8.25 an hour, to support his girlfriend and their two children.
The test Bridger had given was one of a series of benchmark exams that Green Dot uses to measure progress. When the results came, they showed gains: The average score for Bridger's fifth-period class, roughly converted to the state's norms, would be in the low range of "basic," one level below the state's goal of "proficiency." That's not spectacular, but as 11th graders, 63% of Locke students had tested as "below basic" or worse.
Locke's student body includes many who are far behind in credits, others with severe to moderate disabilities, and a small but steady flow of teens returning to school after serving time for criminal activity.
Academic growth over the last year has been uneven, according to Green Dot data. And that has prompted concern. "My nightmare is that the state test scores come in and you're judged by that," said Green Dot founder Steve Barr.