"I was really surprised at the beginning of this year, the number of calls that were with regard to kindergarten students," said Dr. Michael Parker, director of psychological services for Ft. Worth schools. "I had one case with a 6-year-old that was so extreme that the police officer had the child in handcuffs."
In Philadelphia schools, one of the few districts to document violence in young children, there were 42 assaults and 19 weapons possession cases by students in kindergarten and first grade.
"We call it an act 26," said school police officer Ann Johnson. "When the skin is broken, the child is suspended. They are too young to be arrested, so they have a 5 day suspension."
In a Texas study, 93% of school counselors surveyed said that kindergarteners today are experiencing more behavioral problems than kindergarteners five years ago.
"Kids are always getting into fights and stuff, but these calls are aggression toward teachers," said Dr. Parker. "Fighting - not just slapping - but hitting with fists, kicking and biting."
Experts offer the usual reasons for out-of-control behavior: violent video games and television, increased academic pressure and inexperienced parents.
But some educators say there's a phenomenon that parents aren't taking seriously that's as mundane as the dinner table, Assuras reports.
"As I talk with parents, I often find scenarios such as, 'I really don't have time to sit at the table with my child; the food is there and he can eat as he chooses.' So there isn't the interaction that gives the child the discipline," Dr. Parker said.
"They are not coming in with social skills, waiting their turn, being quiet when other people are talking, resolving conflicts without pushing or shoving or biting - or slugging or kicking," said Philadelphia Schools CEO Paul Vallas.
Experts say that if children don't learn how to sit still, they become frustrated and confused in the classroom.
"Children don't differentiate their feelings well. They don't know frustration from disappointment, versus anger. They just get mad," Dr. Parker said.
Some schools are integrating programs like "Second Step," which teaches empathy, impulse control and anger management - behaviors typically missing in violent children, Assuras reports.
At a Long Island, New York, elementary school, Second Step is used to stop aggressive behaviors before they start. Elementary school suspensions at Archer St. School have dropped from 58 kids suspended per year to 12.
"Children get angry the same way adults get angry, but we're trying to get them to deal with their emotions and their feelings," said Archer St. Principal Paula Lien.
As more schools acknowledge the problem, programs are going into place to deal with it, Assuras reports. In Philadelphia, anti-bullying classes start in kindergarten, and kids without pre-school can take special classes to prepare them for school.
Hard data on violence in elementary schools is sketchy, but the warning signs are clear: little problems in kindergarten can grow up to be big problems before long.