According to the latest estimates from the CDC, as many as 1 in 50 kids in U.S. schools have autism. That’s a high number, even higher than last year’s estimate of one in 88 schoolchildren.

The statistic includes all disorders on the autism spectrum, including Asperger’s Syndrome. The study, which compared diagnoses in 2007 (at 1 in 86, according to their study) to those in 2011-’12, attributes “much” of the increase in prevalence to “diagnoses of children with previously unrecognized autism spectrum disorder.” Those diagnosed after 2008 were more likely to have a less severe form of autism, according to researchers. Increases in prevalence were statistically significant for all age groups, and for boys, but not for girls. Boys were four times more likely to have an autism disorder than girls were.

The study relied on parents to report diagnosis, severity, and the approximate date of diagnosis themselves, instead of relying on medical records. The latter, as the Associated Press explains, was the method used by last year’s study resulting in a 1 in 88 estimate for autism diagnosis, leading some to conclude that the current study is less reliable. In any case, the study’s authors are not really arguing that children are more frequently born autistic, only that children are receiving the diagnosis more often:

Together, these findings suggest that the increase in prevalence of parent-reported ASD may have resulted from improved ascertainment of ASD by doctors and other health care professionals in recent years, especially when the symptoms are mild. Changes in the ascertainment of ASD could occur because of changes in ASD awareness among parents or health care professionals, increased access to diagnostic services, changes in how screening tests or diagnostic criteria are used, or increased special education placements in the community.

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