A good seven miles from Gov. Rick Perry's much-anticipated prayer rally, an even larger crowd of Houstonians gathered in preparation for another sacred event: the first day of school.

Some families camped out for hours to gain admittance into Houston's first-ever, citywide back-to-school event at George R. Brown Convention Center, where free backpacks, school supplies, uniforms, haircut vouchers, immunizations and fresh produce were provided.

Others were turned away.

"It was getting beyond capacity," HISD spokesman Jason Spencer said. "If nothing else, it shows the need."

Maribel Martinez and her five children ages 8 to 13 arrived around 7 a.m. to receive backpacks stuffed with supplies including paper, pencils, a pencil sharpener, glue and a compact disc of songs. They also got uniform shirts.

"This is a help, given how the economy is," said Martinez, an East End homemaker whose husband works full-time.

Beatrice Jones, who has two children in the Spring school district, arrived about 10:15 a.m. with her daughter and niece, only to find the doors closed and a police officer announcing the event was over.

"They were supposed to have school supplies, but all we got was sweating and paid parking," Jones said.

School Superintendent Terry Grier posted a Twitter message Saturday morning that security personnel had estimated the crowd at 100,000. At about 10 a.m., officials made the call to close the doors.

Although planners didn't know how many people would attend, they expected to serve at least 25,000 children, officials said.

Paid for with corporate funding from Shell Oil Co. and Motive Enterprises, dental and health checks were also available, as well as lunch and live entertainment.

Diane Mireles said her first priority was the immunization clinic for her two daughters, students at Oates Elementary School in northeast Houston.

"They needed shots to start school," Mireles said, adding that she had no idea where else she would have gone for the service.

Phil Snider came with his 5-year-old grandson, Jayden Celentano, for a bit of school orientation.

"We want to get him inspired, so he'll get ideas about what's going to happen," Snider said of the youngster who starts kindergarten this month at Lovett Elementary in southwest Houston.

Although the crowd inside the convention center had thinned by 11:30 a.m., there was still a long line of people waiting for plastic bags heavy with fresh fruits and vegetables.

The food distribution was organized by Target Hunger, a 27-year-old organization in Houston's Fifth Ward, which partnered with the Houston Food Bank for Saturday's event.

"We'll give away about 50,000 to 60,000 pounds of food before the day is over," said Donna Brownlow, Target Hunger's food services manager.

carol.christian@chron.com