A growing number of children have expressed fears about safety at their schools, particularly in public schools, a new Gallup poll showed.

The poll, taken from Aug. 3 through Aug. 7, also showed parents' concerns for their children have mostly remained steady at 28 percent since 2009, except for a short spike in 2012 after the Sandy Hook Elementary School shooting in Newtown, Conn., that left 28 dead.

Gallup has been documenting parents' level of worry over school safety for some 18 years and found spikes in concern coincide with shooting incidents, including a spike to 55 percent of parents after the 1999 Columbine High School shooting that left 12 students and a teacher dead, and 45 percent after the 2001 Santana High School shooting in California that left two dead.

Gallup researcher Zac Auter speculated the relatively flat response to school violence may be connected to the growing number of school shootings.

"According to the FBI, there have been as many as 50 mass murders or attempted mass murders in U.S. schools since the Columbine shooting," he said in the poll research. "Parents' muted response to high-visibility school shootings in recent years could reflect an increasing desensitization to school violence."

The number of students who have expressed fears about physical safety in their schools is at 13 percent, the highest it's been since 2001 when 22 percent of parents said their children remained worried. In addition, 11 percent of parents with children in public schools say their children have expressed fears over school safety, nearly double the rate of children in private schools (6 percent).

The Gallup poll was based on telephone interviews of 254 random parents with children in kindergarten through 12th grade in the United States. The margin of sampling error is 8 percentage points at the 95 percent confidence level.