01/03/2013 11:40 pm ET Updated Mar 06, 2013

Newtown Parents Express Worry As Children Go Back To School

This photo provided by the Monroe Police Department shows the new Sandy Hook Elementary School on the first day of classes in
This photo provided by the Monroe Police Department shows the new Sandy Hook Elementary School on the first day of classes in Monroe, Conn., Thursday, Jan. 3, 2013. The school, formerly known as Chalk Hill School, was overhauled especially for the students from the Sandy Hook School shooting in Newtown, in the neighboring town of Monroe, Conn. (AP Photo/Monroe Police Department)

By Edith Honan

NEWTOWN, Conn., Jan 3 (Reuters) - The roar of school buses and the sight of bundled-up youngsters dashing out of them for home made a welcome return on Thursday in a neighborhood of Newtown, Connecticut, scarred by the second-worst school shooting in U.S. history three weeks ago.

Classes resumed on Thursday for more than 400 students at Sandy Hook Elementary School. But even as the community inched back to normal, reminders of the Dec. 14 massacre that claimed the lives of 20 first-graders and six adults were everywhere.

For parents of the surviving students, there was a lingering anguish over how much their children understand and how it may have changed them.

Syeda Suriya Ahmed said her 6-year-old son, Mamnun, a first-grader, has suffered nightmares since the shooting. A few days ago, he drew a picture of an adult lying in a pool of blood and told his mother it was a picture of his principal.

Ahmed, who came to Connecticut from Bangladesh 15 years ago, said her son speaks occasionally about the gunman, 20-year-old Adam Lanza, by name. Lanza shot himself dead following the rampage.

"How can he know that?" Ahmed asked. She said she has been careful not to talk about the shooting in front of her son.

A gregarious and playful child, Mamnun said he likes computers, and after school on Thursday he giggled happily as he played with a photographer's camera.

His mother said Mamnun has talked a lot about the shooting.

"He didn't want to go to school this morning. He was scared about the police," Ahmed recalled as she served her son a bowl of pasta as an after-school snack.

Memories of the tragedy continue to haunt Ahmed as well. After first becoming aware that a shooting had occurred at the school, she said she had to wait an agonizing 90 minutes before learning that her son was unharmed.

Once parents were allowed to pick up their children, Ahmed - who does not drive - had to knock on the doors of three neighbors before finding someone who could drive her to the fire station where children evacuated from the school had been taken.

"How can this happen at a school? All those innocent children, how can it happen?" she said.

Anca Roberto said her 5-year-old daughter, a kindergartner, knew only that "something bad" had happened at school. In a way, her daughter was lucky to be young enough so that the magnitude of what happened would not register.

"We talked to counselors about how to deal with this. If she asks, answer. But we don't want to push the envelope," Roberto said. (Reporting by Edith Honan; Editing by Steve Gorman and Lisa Shumaker)