Increased security patrols were in place at some schools as the Monday morning dropoff brought anxiety to countless students and parents.
"[I'm] very concerned," student Donnie Macchia told ABC7 Chicago.
Extra police were visible to ease fears in suburban Riverside. One parent said her children did not want to go to school Monday.
"They said they should be home schooled. So, they're just a little scared because, you know, my daughter is in fifth grade," said Monica Sanchez.
"We want the ones that are scared -- we want to assure them that they're safe and that we're going to do everything that we can to keep them that way," said Lt. William Legg of the Riverside Police Department.
School districts in Chicago and Naperville sent out letters to parents over the weekend to reassure that detailed security plans were in place.
In Oak Park, parents received a letter on Friday reminding them that schools have emergency plans in place and that psychologists would be on hand Monday for any student in need of those services.
Chicago Public Schools officials said grief counselors would also be on hand Monday in the nation's third largest school district.
As Monday approached, some children tweeted online about their fears.
Some psychology experts say parents need to communicate reassurance to their children. They say it is best to be specific and to be brief with kids.
"One of the other really important things for parents to be able to do is they have got to be able to get their kids back to school. They have to reassure them that it's safe. If kids do bring it up, they have to let them know that this is something isolated-- that they will keep them safe and that school is really one of the safest places that children can be," said Dr. Louis Kraus, chief of child and adolescent psychiatry at Rush University Medical Center.
Some parents struggled to carefully explain such a senseless act of violence against children.
"I don't want him not to know. I want him to know what's going on so that he just has an awareness of it," parent Kim Macchia said.
"Her world has been pretty sheltered and pretty great up until this point, and I just want her to know that it's not always gonna be that way. She's gonna have to be careful," said parent Angela Izzo.
Officials also reiterated that CPS safety plans were in place with police officers and counselors set to be deployed to schools as needed.