(RNS) At first, Sarah O'Neal thought the older boy's comment was directed at the towel she was carrying to water polo practice.

"What are you looking at towel-head?" he said.

And that's when it sunk in.

A freshman at Wilcox High School in Santa Clara, Calif., at the time, O'Neal, now 16, marched over and demanded the boy feel her Islamic headscarf. "Does that feel like a towel to you?" O'Neal snapped.

The boy never bothered her again.

Bullying is a nationwide problem, but many school officials and youth workers say it has become especially severe for Muslim students in the 10 years since the 9/11 terrorist attacks. As the new school year coincides with the 9/11 anniversary, some observers worry the problem could worsen.

According to a 2010 survey of Muslim youths aged 11 to 18 conducted by the Washington-based advocacy group Muslim Mothers Against Violence, all 57 respondents reported being called a name because of their faith, including 80 percent who said they had been called "terrorist."

While there are no firm statistics on how many or how often Muslim students are bullied, activists assert it is higher than other students because of post-9/11 Islamophobia. Responding to bullying can be especially complicated because of immigrant parents who may be intimidated by bureaucracies, or because adults charged with protecting students might be part of the problem.

As an eighth-grade student at Beckendorf Junior High School in Katy, Texas -- the same town where residents infamously held pig races to protest a proposed mosque in 2006 -- Abdul Hamed initially accepted a classmate's explanation that jibes like "terrorist" and "you're family blows things up," were just jokes.

But the teasing continued almost daily, and soon escalated into shoving.

Abdul alerted his teachers, who separated the boys in class, but the bullying would continue in the hallways. In early February 2009, on the school's track field, Abdul shoved back.

According to Abdul, the boy left but returned several minutes later and sucker punched him, knocking him out and breaking his jaw. That was how Abdul's Palestinian immigrant parents first learned about the bullying.

Abdul said school officials made the boy go to anger management counseling. "For what I went through, that punishment wasn't even close," said Abdul, whose jaw was wired shut and missed several weeks of school.

Abdul, now a 15-year-old sophomore at Seven Lakes High School where his attacker also goes, said he's moved on.

While ethnic, racial and religious bullying is not new, observers say Muslim American students face the added challenge of having to defend themselves against television images of American soldiers fighting terrorists in Muslim lands.

"Muslim kids are bullied for geopolitical reasons," said Pia Britto, a professor at the Child Study Center at Yale Medical School. "They're being bullied because this larger media portrays people of their religion in a negative way, and these young kids have to stand up against this portrayal, which is a different dimension of bullying."

Britto said kids use the "terrorist" slur "all the time," which can be harder to respond to than other taunts. "If you react you're fulfilling the taunt," she said, "and if you don't react you get angry and resentful that your hands are tied."

Despite the increased attention on bullying since a spate of teen suicides highlighted the problem a year ago, news reports and academic studies document dozens of examples in which school officials have dismissed Muslim bullying complaints. In some instances, teachers themselves are the bullies.

Among other examples, a substitute teacher at a school in Hillsborough County, Fla., was disciplined in 2007 for harassing a sixth-grader because his name was Islam. In 2006, a substitute teacher in Gaithersburg, Md., had to be escorted from a school after berating a group of students for speaking Arabic.

"A lot of times the teacher has the same viewpoints and takes the bully's side, and somehow views that the Muslim kid is responsible for violence that has been committed against the United States," said Maha ElGenaidi, executive director of the Islamic Networks Group in San Jose, Calif., which develops anti-bullying curriculum programs.

For her part, Sarah O'Neal said reporting the "towel-head" comment to school administrators probably wouldn't have done much good. After she started wearing the hijab in sixth grade, someone spray-painted "Sarah O'Neal is a terrorist" inside a school bathroom. She told the assistant principal, who later also met with Sarah's mother, but the school never documented or investigated the incident. Sarah said she still doesn't know who did it.

Muslim youth workers say many parents don't know their children are being harassed. Groups that try to combat stereotypes or misconceptions about Muslims in school say they also have to teach Muslim kids how to respond.

"A lot of it is self-esteem," said ElGenaidi. "If they're not confident of what they're about or what they're parents are about, it's very difficult for them to defend against the difficult questions that they get asked."