With cheerleaders, mascots, and thunderous applause, thousands of students from Mastery Charter Schools gathered for a giant pep rally Monday, but the event had nothing to do with sports.

It was "College Signing Day," held to celebrate the academic success of 450 high school seniors heading off to pursue degrees in higher education.

"We believe you will be the ones . . . to change the world and change this city," said Scott Gordon, Mastery Charter Schools' chief executive, as he addressed students from five high schools who had gathered at Temple University's Liacouras Center.

The seniors sat in chairs on the floor while about 5,000 students from lower grades cheered from the stands.

Amid a greeting befitting a rock star, Gordon told the students: "You are the real rock stars." He then led the crowd in chanting the schools' motto, "Excellence; No Excuses."

After listening to speakers who included Mayor Nutter, the students signed large cards, pledging to complete their college degrees or other postsecondary programs.

The names of the students and the 85 schools they will attend were displayed on an electronic sign that circles the arena.

"The most important folks in the room today are our graduates," said Nutter, who congratulated the seniors but told them hard work was ahead.

"You know your journey is not done. . . . You know you have more to do," he said. "In four years, I want to see you graduating from those schools."

Mastery Charter Schools is a nonprofit organization that operates 12 schools in Philadelphia serving 8,000 families.

In operation since 2001, Mastery runs five high schools: Mastery Charter Lenfest Campus in Center City, Mastery Charter Pickett Campus in Germantown, Mastery Charter Thomas Campus in South Philadelphia, Mastery Charter Shoemaker in Southwest Philadelphia, and Simon Gratz Mastery High School in North Philadelphia.

Tracy Delarge, whose daughter Brittany Isaac is graduating from the Pickett campus and plans to study psychology at Bloomsburg University in the fall, said she was thrilled to attend the event.

"This whole ceremony, I think, is great," Delarge said. "I am excited and proud."

Delarge said Brittany was the fourth of her five children to go to college or other postsecondary school and the third to graduate from a Mastery charter school.

"This should be encouragement for the ninth, 10th and 11th graders, just to be a part of this celebration," Delarge said.

Shamina Stevens of West Philadelphia, a senior at the Lenfest campus, called the celebration "very encouraging."

Stevens, who will attend Bloomsburg in the fall to study finance, said she was "not at all intimidated about going to college, because Mastery prepared me in every way."

Eric Knight, head of the parents association at the Lenfest campus, said the program was an inspiration to underclassmen at Mastery schools.

"I think this is simply amazing," said Knight, whose son, Trevor, attends ninth grade. "I think the setting was very appropriate." He said the program gives young students "the bigger picture. This is what education is all about."