Alex Arriaga plays with her son, Tommy, April 27 at Alcove Park in Arlington. Arriaga has been a driving force for a bill being introduced by Rep. Jim Moran to help train teachers to deal with autistic kids. (Dayna Smith/FOR THE WASHINGTON POST)

When pediatricians started questioning Alex Arriaga about the development of her infant son, she struggled to understand why.

“Some of the things that they told us were really kind of nutty,” Arriaga recalled. “At about 8 months: ‘Is he talking yet?’ Well, no, but he’s 8 months, and he was premature, so give him a break.”

When Tommy was diagnosed with an autism spectrum disorder at 18 months, Arriaga was even more incredulous.

“It was one of those things that was just shocking,” she said. “Honestly, my husband and I were very skeptical. . . . At the same time, we thought, ‘These are professionals.’ ”

The next surprise came after Tommy started public school in Arlington County. Arriaga realized what a growing number of parents, activists and school administrators have learned: The population of autistic children is fast outstripping the number of teachers trained to handle it.

“You’re sort of catapulted into this world where you feel like you need to learn as much as you can, because you will be your child’s advocate,” Arriaga said. “And you may get a good teacher, but you just don’t know.”

So the politically savvy Arriaga, a former White House and congressional aide, joined other Northern Virginia parents in approaching Rep. James P. Moran Jr. (D-Va.). Their lobbying efforts bore fruit Friday, when Moran introduced legislation that would begin addressing that shortfall.

The AUTISM Educators Act would create a five-year grant program to train general-education classroom teachers on the best ways to identify and interact with students with autism spectrum disorders. While children with extreme forms of autism often require separate special-education classes, many with milder cases are mixed into the general population.

The grants would be targeted at school systems with high autism rates — 10 percent or more of the district’s special-education population — and would require the systems to partner with a university or nonprofit group to develop the training program.

That description neatly depicts Arlington, which has teamed up with Virginia Commonwealth University to provide autism training to some officials.

Arlington School Board Chairman Abby Raphael said that in 2003, there were just more than 100 students in the county identified with autism spectrum disorders. As of this year, that number had risen to 361 students — or 11 percent of the county’s total special-needs population — and by 2015, the number is projected to top 500.

That rapid growth mirrors a national trend. A Centers for Disease Control and Prevention survey released last month showed that the prevalence of autism has increased nearly 80 percent over the past decade. About one in 88 U.S. children (and one in 54 boys) has autism.

On one level, it’s a simple math problem: The number of children with autism is growing quickly, but school funding levels aren’t.

“It really comes down to budget,” Raphael said. “We provide lots of development for our teachers, but there are limited resources to do that.”

Erin Stone, the autism coordinator for Alexandria public schools, said that with so many autistic students in non-special-education classes, “general-education teachers and principals have expressed concern that they are inadequately prepared to handle some of the behaviors” of autistic children.

Moran offered the bill with Rep. Mike Doyle (D-Pa.), the co-chairman of the Congressional Autism Caucus. They hope to add Republican backers soon.

“The teachers are begging us to do something like this,” Moran said. “The school system is very receptive, and the parents obviously are the most focused. . . . Everybody likes it; so I’ve got to build bipartisan support.”

Moran’s bill would move as part of a broader rewrite of the No Child Left Behind Act. That measure is scheduled for reauthorization this year. But nothing moves easily through the divided Congress, so it’s not yet clear whether the autism legislation has a good shot at becoming law.

Arriaga knows Capitol Hill, and she knows politics — she quit her job as head of government relations for Amnesty International to spend more time helping Tommy — but she is hopeful that the need for action will help her cause.

When he turned 2, Tommy entered a preschool program for children with autism and spent three years getting what Arriaga called “very intensive” attention with teachers who were familiar with autism spectrum disorders.

But the story was different for teachers in the regular preschool classes on the same campus. “Privately, a lot of teachers would come up to me and say, ‘I have a degree in special education from 25 years ago, and we didn’t focus on autism,’ ” Arriaga said.

She and her husband made sure Tommy spent some time in the adjoining, regular classroom. But that was a challenge, because “if you just put him in there, he doesn’t know how to say, ‘Do you want to play?’ . . . He doesn’t know how to say, ‘What’s your name?’ ”

By the time Tommy entered kindergarten, Arriaga said, he had made “huge advances,” and it was clear “he would benefit from being in a general-education class with the proper support.”

Arriaga and her husband are happy with her son’s kindergarten class and his teacher. But they have heard from other parents about classrooms where the teachers and aides simply have too many children to give the proper attention to those who need it.

“There’s a recognition that there’s a wave coming,” Arriaga said, “and what can we do?”