Researchers seeking alternatives to the use of drugs to treat ADHD in children are taking a closer look at exercise as a prescription.

A recent study found regular, half-hour sessions of aerobic activity before school helped young children with symptoms of attention deficit hyperactivity disorder become more attentive and less moody. Other research found a single bout of exercise improved students' attention and academic skills.

It isn't clear whether physical exercise offers particular benefits to children with symptoms of ADHD, since students with typical development also showed improvements after the sessions. Children with the condition have greater-than-normal difficulty paying attention and may exhibit impulsive behavior, among other symptoms.

Some doctors who specialize in treating children diagnosed with ADHD say they often incorporate exercise in the therapy. And some teachers have begun getting students up from their desks for short bursts of physical activity, finding it helps them pay attention to their studies.

"It benefits all the kids, but I definitely see where it helps the kids with ADHD a lot," said Jill Fritz, a fourth-grade teacher at Rutledge Pearson Elementary school in Jacksonville, Fla. "It really helps them get back on track and get focused."

Growing numbers of children in the U.S. have been diagnosed with ADHD. The Centers for Disease Control and Prevention calculated 11% of children had an ADHD diagnosis in 2011, the latest data available. That was up from 7.8% in 2003. Among all children in the U.S., 6.1% in 2011 were taking an ADHD medication, such as Adderall and Ritalin, up from 4.8% in 2007.

In a study published online Tuesday in the Journal of Abnormal Child Psychology, students in kindergarten through second grade did 31 minutes of aerobic physical activity before the start of school for 12 weeks. Another group of students engaged in a sedentary, classroom-based activity. The study, conducted at schools in Vermont and Indiana, involved 202 students.

Click for more from The Wall Street Journal.