The DuPage County state's attorney, the mayor of Darien and others joined school officials at the meeting.
They fielded questions about what transpired last week.
"I am a community member and parent, and my heart stopped last Thursday," District 86 School Board President Catherine Greenspon said.
Authorities say last Thursday, at Hinsdale South High School, a 16-year-old male student from Willowbrook brought a loaded 9mm handgun to class.
The district said it learned of the weapon and notified police, who arrested the boy without incident. He's been charged with two felony weapons counts, including aggravated unlawful use of a weapon. A judge ordered he remain in custody until his next court appearance.
"The student was later escorted to the dean's office, at which point administration and security became aware that the student had a gun, and called 911. In 47 seconds, armed security was on the scene and had possession of the gun," District 86 Superintendent Michael Lach said.
Following the incident, the district said it's put in place a screening system at the school that's generally used for large school events, including football games.
"We told the community that we would use our weapons detection system through at least the start of Thanksgiving break, which is coming up here on Wednesday. So, we committed to doing that, and we'll further explore our options as we progress," Hinsdale District 86 Spokesperson Alex Mayster said.
District officials say their security protocol worked well in this incident, but some parents at the meeting disagree, and want stricter measures put in place.
"How could somebody walk into a school for three hours with a weapon loaded?" one parent said.
Some want the screening system in place permanently.
"We're in an age that we have to take all measures possible to keep the kids safe, and I'd say using a metal detector would be the first step," parent John McPherson said.
But others aren't so sure.
"Several parents have also called me, and said they don't want that to happen because they're worried about the implications," Lach said. "They are worried about a 'police state.'"
Authorities have not said why that student brought that gun to school. The district said it was unaware of any threats that were made, but referred all questions about the investigation to police.