It has been exactly 11 years since the tragedy at Columbine High School where 12 students and a teacher were gunned down by Eric Harris and Dylan Klebold.

The mass murder set off a national push to increase school safety and security. But how far have we come since then?

Zero tolerance laws went into effect in Texas schools starting in 2000, the year after Columbine. Houston Independent School District takes terroristic threats, drugs and guns with deadly seriousness. Offenders often face severe punishments. But post-Columbine rules can sometimes lead to overreaction also.

In 1999, Harris and Klebold changed the face of American high schools forever.

"In the cases of bullying you want to make sure you're responding immediately, because if you push it away and something does happen it's Columbine all over again," said Peter Messiah, HISD safety manager.

HISD follows zero tolerance when it comes to threats and weapons.

"Very severe," said Messiah of the punishments zero tolerance offenders can face. "They can go to out-of-school placement, they could go to a DEAP, they could be on suspension. We take it very seriously and they have immediate consequences."

Gayle Fallon, president of the Houston Federation of Teachers remembers incidents in the pre-Columbine days.

"Fortunately he listened when I said, 'you put that gun in my desk drawer right now,"' said Fallon of a particular incident from her teaching days.

She said while security's gotten better, sometimes it's still not enough in Houston.

"If anything, in HISD, the administration often under-reacts to problems. It takes a lot to get a child removed from campus other than catching them with the gun on them or drugs on them," said Fallon.

But all the extra attention to safety has led to paranoia in some cases. Last week a Cy-Fair ISD teen was suspended for pointing a finger-gun. The teacher took it as a threat while the teen said it was a harmless joke because she was wearing a shirt that said NYPD.

"In the suburbs they do tend to over-react," said Fallon. "That's where we hear the parents screaming about zero tolerance because, 'my kid didn't have a real weapon in his pocket, he had a nail file or forgot he had his pocket knife in his pocket."

And according to Fallon, overreaction can cause its own problems when it comes to safety in schools.

"When you do that you have irate parents who are up at the legislature attacking what is good legislation and good public policy, because of abuses," she said.

HISD said one of the biggest changes schools have seen since Columbine is parents wanting kids to have cell phones on campus in case of emergency. Before Columbine few schools allowed cell phones on campus.