Chicago Mayor Rahm Emanuel says the NRA's desire to have an armed officer in every American school is "outrageous and unsettling."
"That is not the right answer for our society, our schools and most importantly our children," he said in a statement issued Friday.
The mayor said the answer to America's gun violence is a reduction in the number of arms in society, not adding more guns to schools.
"People across this country, from small towns to big cities, are united and ready to pass common-sense gun control legislation. The time has come for the NRA to get on board or get out of the way," said Emanuel.
Earlier in the day, the country's largest gun-rights lobby called for an armed guard in every school to stop the next killer "waiting in the wings."
Emanuel on Thursday gathered 22 area mayors and echoed his call for a ban on semi-automatic weapons, for a restriction on the size of bullet clips and for more complete background checks on gun purchases.
"In order to protect our children, our families and our communities, we need commonsense gun-control legislation," he said. "I urge other city leaders from throughout our state and the country to join our cause."
Rep. Mike Quigley (D-IL-5) on Friday called the comments of NRA Executive Vice President Wayne LaPierre "a joke, thoughtless, meaningless, an afront, not just to the victims of Connecticut but for every crisis we've faced."
Gov. Pat Quinn proclaimed Friday a day of mourning for Illinois in a show of support aligned with a moment of silence across the country to honor those lost in the Connecticut school shooting a week ago.