It's been five years since the crackdown, and researchers found high school students are eating an average of 160 calories fewer calories a day than kids in other states, a trend that could help reverse obesity trends. They're also eating less fat and sugars.
"Studies are really showing that we sort of stopped the growth in the obesity epidemic, that it's leveling off, and so hopefully these kids are taking a stronger interest in nutrition and their health," said nutrition specialist Anne Gaffney.
California school campuses don't sell sodas, unhealthy snacks and fried foods. You'll find fruits and vegetables, French fries that are baked and whole grains. Schools have even gotten rid of salt packets.
"At first, I was kind of upset because I like salt. But it's helping me eat a lot better. And that's what I actually want to do," said Diana Nagtalon, a high school senior.
While 160 fewer calories a day may not be much - it's like a small bag of chips - researchers say most children could avoid significant long-term weight gain by simply cutting out 100 to 200 extra calories a day.
Students do bring junk food from home, and they consume only 25 percent of their calories at school. Assemblyman Richard Pan, who's also a pediatrician, says more needs to be done.
"We've just show that in the school, we've created an environment where kids will then take fewer calories. We can now use this information to talk to parents about how do we create the environment at home," Pan said.
The study's author also noted the findings are encouraging for the Hispanic community, considering the high prevalence of obesity among Latino youth