Thousands of students around the Philadelphia region joined counterparts nationwide in a walkout to protest gun violence Wednesday morning, a month to the day 17 people were killed in a shooting at the Marjory Stoneman Douglas High School in Parkland, Fla.

The  #NationalSchoolWalkout officially began at 10 a.m. Organizers had called for the protests to last 17 minutes in honor of the Parkland victims, but some lasted longer, including a march by students on Philadelphia's City Hall.

At Philadelphia's Central High School, the second largest school on the city, students chanted "No guns!" and "Enough is enough!"

After speeches, many of the students headed to the Philadelphia School District's offices at 440 N. Broad St. for a rally followed by a march to City Hall.

"The NRA is not ok!" and "Books, not bullets!" the students chanted as they marched down Broad Street to City Hall.

At City Hall, they chanted, "Hold hands, not guns" and "We stand together! We stand forever!"

Hundreds of students earlier took part in the Central High protest.

Students at Cherry Hill West High School walked out about 9:30 a.m. and later returned to classes.

At Lower Merion High School, the walkout started at 10 a.m. After a period of silence the students gathered for speeches.

This was the scene at the Workshop School in West Philadelphia, where the motto is "Teaching students to change the world."

The walkout at Atlantic City High School was called off after the school was locked down for what was described as an "active police investigation."

Hours before the protest was set to begin, another South Jersey school district canceled classes for the day after Harrison Township reported an anonymous potential threat against Clearview Regional High School.

>> READ MORE: 'This is only the beginning': Students' views of the National School Walkout

>> READ MORE: How school districts responded to the walkout

The Clearview Regional School District, which has about 2,500 students in grades seven through 12 from rural Harrison and Mantua Townships, said in a statement that county sheriff's department and New Jersey State Police canine units conducted a sweep of the school building overnight but found no weapons.

Still, the district said, the school would be closed Wednesday "due to the lack of specificity to the threat."

Meanwhile, Nikolas Cruz, the 19-year-old charged in the Parkland mass killing, also is due in court Wednesday for a hearing after prosecutors announced they would seek the death penalty against him.

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