SAN DIEGO -- Thousands of protesters -- mostly teenage students -- took to the streets throughout San Diego County on Monday to voice their opposition to an immigration bill being debated in Congress.

One of the largest and most boisterous demonstrations occurred in Escondido, where hundreds of youths from Orange Glen and San Pasqual high schools marched along streets and chanted in front of City Hall, police said.

Escondido police requested backup personnel from other agencies, said Lt. James Bolwerk of the county sheriff's department, which sent in a group of motorcycle officers to help keep the peace.

Similar rallies -- prompted by a bill that would crack down on employers hiring illegal workers and people smuggling illegal immigrants into the country -- took place throughout the county, Bolwerk said.

By midday, law enforcement personnel reportedly had taken several people into custody for failing to disperse. Precise arrest numbers were not immediately available.

In San Diego, about 300 students from at least three public secondary schools -- Gompers, Mission Bay and San Diego High -- walked out of classes and joined a march to Chicano Park, said district spokeswoman Music McCall.

"Our school police officers are on scene, as are SDPD officers, to provide traffic and pedestrian safety," she said at midday. "We have at least one site administrator keeping track of the students and requesting that they return back to school."

Those participating in the walkout were "considered to be in defiance of district rules" and will be subject to discipline, possibly including detention or suspension, McCall said.

Illegal immigration is also the center piece of most candidates running to replace ex-U.S. Rep. Randy "Duke" Cunningham.

At a breakfast honoring Cesar Chavez at the San Diego Convention Center, his son, Paul Chavez, said the activism he sees across the country is something his father would have been proud of.

"That's what he worked for, to have people get up and say they are for this or against that as people marched in Phoenix Friday and in Los Angeles Saturday and Sunday. I think my father would be smiling down on all of us," said Paul Chavez.

The disputed immigration bill, introduced by Rep. F. James Sensenbrenner, R-Wis., would require employers to verify Social Security numbers with the Department of Homeland Security, increase penalities for human smuggling and stiffen punishments for undocumented immigrants who re-enter the United States after being deported.

Under the legislation, local law enforcement agencies would be reimbursed for detaining illegal immigrants. Refugees with aggravated felony convictions would also be barred from receiving green cards.

The House of Representatives approved the bill in December. The Senate was debating the legislation Monday.