More than 97,000 California public school students have been diagnosed as autistic, a number that has risen seven-fold since 2001, according to the latest special education data from the California Department of Education.
The figure represent a jump of about 6,500, or 7 percent, from 2014-15 to 2015-16.
The increase was especially sharp among kindergartners, where autism cases grew by 17 percent last year. More than one of every 65 kindergartners in California public schools is classified as autistic.
Since 2006, the number of autistic students statewide has risen by between 5,000 and 7,000 every year, state figures show.
In the four-county Sacramento region, the number of autistic students rose by about 660, or 12 percent, to roughly 6,400 from 2014-15 to 2015-16.
Theories for the rise, which has been seen nationwide, include improved autism screening, broader definitions of the condition and more children who were either born with autism or who developed the condition due to environmental factors.
Fears that modern vaccines cause autism have led some parents to forego vaccinating their children. The American Academy of Pediatrics says no evidence exists linking autism to vaccines. A new state law eliminates "personal belief exemptions" allowing parents to opt their children out of vaccinations before starting school.
This chart shows the number of students with autism statewide since 2001.