At a better school, in a less desperate part of the city, Zeus Cubias might have shrugged off the disruption.
But after a decade teaching at Locke High School -- one of the worst in the Los Angeles public school system -- he was annoyed when a recent geometry class ended with one more small reminder of how much things need to change.
Cubias had wolfed down his lunch and hustled back to his room for the start of class. He launched enthusiastically into a special two-day lesson he had devised.
"All right, your job is to paint the school," he said, his voice raspy from a morning of classes. "How can we use geometry to figure it out?"
The hour passed quickly as talk turned to angles, protractors and calculating area. A minute before the bell was to sound, Cubias warned his students that they would need a quick start the next day in order to finish the assignment.
"Sorry, Cubias," one student called out, "I won't be here. Field trip to the beach."
"Me too," a chorus of others chimed in.
Standing at the front of the room, the teacher bowed his head and rubbed his eyes wearily -- the frustration welling up. Half his students would be absent the next day, and no administrator or other teacher had bothered to tell him. The lesson he had designed would have to be postponed.
"I'm just tired, man," he said later. "Tired that whenever you want to do something positive for the kids, it's a struggle. It shouldn't be this hard."
Cubias is symbolically at the center of a power struggle taking shape in the mammoth Los Angeles Unified School District, the nation's second largest. With a prominent charter school organization challenging the district for control of Locke, the school's teachers ultimately must decide which is better able to deliver badly needed reforms.
The direction that Cubias and the rest of the faculty choose could have far-reaching implications for L.A. Unified, as teachers at other schools consider similar options.
The charter group, Green Dot Public Schools, shocked district officials in May when it announced that a majority of Locke's tenured teachers had signed petitions in support of a Green Dot takeover, clearing the major legal barrier to converting the campus into several independent schools.
District officials countered with promises to teachers of increased authority and reforms if Locke remained within the district. After several teachers rescinded their signatures, saying they were confused about the takeover proposal, district officials threw out the formal takeover plan submitted by Green Dot.
Recent days, however, have brought a shift in direction at the district headquarters as a new school board majority allied with Mayor Antonio Villaraigosa has taken control. On Tuesday, new board member Richard Vladovic, who represents the Locke area, presented a motion to require an up-or-down vote in August on the Green Dot petition.
The charter group's leaders have vowed to press ahead, one way or another, with plans to convert Locke by 2008. Green Dot is planning to open two small charter schools near Locke this fall. To propel this effort, the Bill & Melinda Gates Foundation announced Monday that it had given Green Dot an $8-million grant to develop charter schools in the Locke-Watts area.
The battle over charter schools has roiled Locke. Some teachers angrily oppose a takeover, while others are eagerly supportive. Many remain undecided.
For Karen Brown, who has taught at Locke for 16 years and heads the school's widely respected fashion design program, Green Dot is nothing more than an unproven, uninvited group attempting a hostile takeover.
She and other longtime Locke teachers are suspicious of Green Dot's labor contract with its union, which does not include the detailed work rules, job protections or lifetime benefits granted district teachers. Moreover, those teachers reject the idea that Locke is broken.
"We are confident that we can continue to give our students what they need. We don't need anybody from the outside coming in telling us how to do our job," Brown said. Green Dot "cannot prove to me that they can do a better job. Not here."
For Cubias, 32, a Locke graduate who grew up in the poor, violent neighborhoods surrounding the South L.A. campus, the field trip debacle reflected larger problems at a school he sees as struggling in an ineffective district. Much of the charter school's model appeals to him.
Green Dot's plan for Locke calls for the large campus to be divided into several small, autonomous schools with separate faculties and principals.
With a small central office and administrative staff for their schools, Green Dot officials say, they funnel more state funds into classrooms than the district does and give teachers and principals considerable control over budgets and instruction.