St. Louis ? When it’s hard to breathe, it’s hard to stay in school, play with friends and just be a kid.

A mobile asthma clinic run by St. Louis Children’s Hospital travels to 13 elementary schools around St. Louis to test kids for the lung disorder and check in with those who have already been diagnosed.

At some schools, nearly a quarter of kids are asthmatic. That’s three times higher than the national average, and combined with St. Louis’ ranking as the most dangerous place for people with asthma, you get lots of kids struggling to breathe.

Kids like Tevin Tourville, 13, who often sits on the sidelines when his friends are out playing.

Tevin visited the asthma van recently at his school, Lucas Crossing Elementary in Normandy. There, a nurse reminded Tevin that he can inhale his albuterol and open his airways before exercise to keep him playing longer.

Last year, 727 schoolchildren received asthma treatment through the Healthy Kids program. The new asthma van joins two other roving clinics that test kids’ vision and hearing and offer immunizations for free thanks to various grants.

The van travels to Lucas Crossing more than any other school, since about 200 out of 800 students there are thought to have asthma. All the schools in the program have reported a reduction in absenteeism by an average of 13 percent.

Asthma is generally controllable, but it’s hard to get kids to comply with complicated drug regimens and breathing exercises. The nurses on the van remind the kids about how and when to use their inhalers.

Joan Upperman, a nurse and respiratory specialist who works full time on the van, said the kids inspire her because with “all of their challenges they just keep going.”

Each kid with asthma is seen on the van at least three times during the school year. It helps them recognize their asthma symptoms, manage their medications and reduce school absences, said Lucas Crossing school nurse JoAnn Mills. “Without it I don’t see how we would have been able to safely manage the illness,” she said.

It’s dangerous not to. Chronic respiratory disease, including asthma, is the fourth-leading cause of death in the St. Louis area. Emergency room doctors say they have seen children in asthma attacks who have never before been treated.

This year, the Asthma and Allergy Foundation of America named the St. Louis region the nation’s worst for asthmatics, based on factors including an above-average death rate from asthma, a lack of smoke-free laws and high pollen counts.