Teams of armed officers in fatigues and bullet proof vests move cautiously through Homestead's white buildings, their rifles raised. "Suspect down in B Building," says a voice on the radio. "There's an innocent down on the top floor, that's B as in Bravo."

Fortunately, this is just a drill. The shots are bursts on an air horn. The suspect and victims are police officers role playing, and officers use guns with barrels wrapped in blue tape, and without ammunition.

"The goal is to practice what to do in an actual situation," Principal Graham Clark said. "We want to make it as real as possible, so we can practice what to do."

School Resource Officer Jim Post said the exercise was to prepare for any shooters on campus, from angry students to parents involved in custody battles. Post said the shootings at Columbine High School in Colorado in part inspired the drill. "After Columbine, we realized we couldn't just set up a perimeter and wait for SWAT teams to arrive, " he said. "So we have trained our beat officers to arrive on site and immediately take action." Sheriffs from Cupertino and Saratoga and officers from Sunnyvale's Department of Public Safety all contributed to the drill.

In this training scenario, three suspect shooters are on campus. Teachers are informed through loudspeakers a 'Code Red' is in effect. Teachers and students have been trained to barricade their classrooms with desks, tables and shelves blocking the door, and to create a second barricade inside the room.

As the police sweep the building, students and teachers huddle behind their improvised barricades.

The training serves both the police officers and the school's staff and students.

Students and teachers are not supposed to know a "Code Red," the school's name for the drill, is in effect. However, the nearly 50 sheriff's officers in the parking lot before the sound of gun shots is a tip off.

The parking lot serves as a staging ground and command post for the exercise. From there, three teams of officers in diamond-shaped formations move carefully through the campus following the sound of air guns. School administrators and police supervisors monitor their progress. After the drill, school staff and police officers will receive critiques of their performances.

Principal Clark hopes the seriousness of the drill is instilled in the students.

"We're trying to get them to take it seriously," he said. "The students tend to kind of blow these things off."

"It's great for the sheriff's officers to work with the school staff," Post said.

There is still room for improvement. At the end of the exercise, there was confusion about which buildings had been cleared. A few teachers had also released their students early, and they wandered among officers still drilling. Other teachers left classrooms and hallways vulnerable due to poorly constructed barricades.

Even so, police and school administrators are pleased with the results, especially since it is the first time the drill has been practiced at Homestead.

"In a situation like this, there is no real success," said Lieutenant Terry Calderone, a supervising officer. "In this case there was only one [mock] student casualty so I would say it was very successful."

"Just having it is a success," agreed Assistant Principal Paula Bassett.