Danilo Rubio, 17, rolled up his plaid shirt sleeves, bared both arms and gritted his teeth. "My son wants the biggest needle you have," his father joked in Spanish as the nurse laid out three vaccine syringes and a tuberculosis test. Four pricks later, it was over.

Danilo's brother Jose, 14, next in line, wrinkled his nose as his turn approached. "Oh, that's a big one," his father said melodramatically, staring at one syringe. Jose furrowed his brow.

"Don't be afraid," his older brother said.

Danilo and Jose were among about 200 students getting free or low-cost physicals, vaccinations and hearing and vision examinations at the Upper Cardozo Community Health Center, a busy clinic that serves the heavily Latino neighborhoods of Mount Pleasant and Columbia Heights in Northwest Washington.

The clinic also offered 120 dental screenings to youths to prepare for Monday's reopening of D.C. public schools. For some recent immigrants, the visit marked their first U.S. medical appointment and a way to find a primary care doctor.

The school system requires proof of vaccinations along with yearly physicals and dental screenings before students are admitted to class. Clinics across the city have provided those services all summer, but the Upper Cardozo center, as well as one in Congress Heights in Southeast, set up a back-to-school push for youths who still needed them.

That was no small number.

A jam of kids and parents with smaller children in strollers clogged the entrance and stretched around the side of the building well before the 8 a.m. opening. All 200 slots were taken by midmorning.

"We scheduled it as a walk-in day because we deal with an immigrant population. . . . They often have changing jobs, schedules and locations," said Danielle Dooley, a pediatrician who performed physical exams. The event began this year because appointments for summer physicals were filled, despite scores of kids who still needed them.

Sixty-five to 80 percent of young people who use the clinic are Latino, and some health issues are more common for them, said Rachel Tellez, also a pediatrician at the clinic. Language barriers and a higher illiteracy rate than in the general population mean that fewer parents expose children to books early on, which leads to higher rates of speech delay that can create difficulties at school. Also, "when they start school at 3 or 4 years, they begin to forget their Spanish," said Tellez, so some youths begin to have trouble communicating with their parents.

Another important consideration for Latino youths is help with family adjustments, said Dooley, because parents often bring their children to the United States after living here for years and establishing new lives. Young people, particularly teenagers, sometimes suffer emotional stress because they have been separated from their parents for a long time and might only recently have met younger siblings.

Common physical ailments include obesity and asthma, which is widespread because of dusty, insect-infested housing, Dooley said. As for obesity, "a healthy child is associated with a child that weighs a lot, because they come from malnourished societies. It's a sign that they can provide for their kids," Dooley said, adding that doctors must educate parents on nutrition.

One of Dooley's patients yesterday was Amilcar Navarro, 10, who came from El Salvador last year. Dooley was the first doctor he saw after immigrating. She asked in Spanish whether he wears his seat belt, how much milk he drinks, how often he brushes his teeth and how much time he spends watching television. As she listened to his lungs and heart with a stethoscope and examined his belly, he giggled and squirmed.

His mother was concerned about his knees, which she said hurt after he plays soccer, so Dooley printed out information in Spanish on knee pain. Then Amilcar told her about the summer program for high-achieving students in which he participated and smiled widely at her praise.

Dooley filled out her portion of the school form, and Amilcar headed to his dental exam. Soon, that too would be finished, and only the results of his tuberculosis test would remain between him and school.

Fifth grade awaited.

Ana Hernandez, 9, a recent arrival from El Salvador, prepares for school by getting a shot at the Upper Cardozo Community Health Center.Angelica Corona, 9, left, and Esmeralda Valencia, 8, play a game in the waiting room before their physical exams are performed. Wanda Donado, 11, left, waits at the clinic with her sister, Ashley Hernandez, 9. The girls joined the line at 8:30 a.m. By midmorning, all 200 slots were taken.Physician Danielle Dooley, left, speaks in Spanish with Amilcar Navarro, 10, and his mother, Marta Navarro. Dooley asks whether Amilcar wears his seat belt, how much milk he drinks and how much time he spends watching TV.