But not in Maryland.
In Prince George's County - home to the youngest victim so far, 13, the only one attacked on school grounds - school officials said they learned of the specific threat to children only when they saw Montgomery County Police Chief Charles A. Moose on CNN yesterday. Only then did they have all the information - and decide schools would open again today.
That wasn't the decision some parents would have liked.
"I feel I have to take my daughter home as fast as I can," said Pichai Kulprasertrat, who picked up 11-year-old Melissa before the day had ended at Argyle Middle School, barely a mile from where a 35-year-old bus driver was killed before dawn yesterday. "If they had closed, I would have felt a lot better."
The kids were getting antsy and wanted to run around outside after school; some were getting into fights. Though the sniper has killed five in Montgomery County, he hadn't killed anyone there since Oct. 3, nearly three weeks.
"When I turned on the news this morning, it was all I could do not to burst into tears," said Silver Spring resident Michelle Turner, a mother of five children ages 7 through 16. "People were maybe lulled into a false sense of security thinking he'd moved 100 miles south of here."
In the areas surrounding Aspen Hill, many of the schools had just half of their students show up for class yesterday. At Strathmore Elementary, barely a mile from the site of the most recent attack, only 10 percent of the school's 822 students came to school, said school system spokesman Brian J. Porter. Attendance was good in schools farther away, he said.
Getting to school - for both students and teachers - was a massive headache. With traffic backed up for miles in many directions and intermittent roadblocks along the way, some schools opened with just a handful of faculty members.
The lights were turned off. Students were told to sit either on the floor or under their desks or were corralled in the gymnasium for safety. Students were forbidden from walking home, parents said.
Police responded in force by land and by air, and "it's believed to be a false alarm," Porter said. "That community had already been pretty well jittered by the ongoing events."
Dewitt Wood Jr. picked up his fourth-grade son, Dewitt III, at Strathmore. "I think they should have closed schools like Virginia did," he said. "If I were the superintendent, I would have made the call at least for a day or two. ...
"I guess they're thinking we don't want [the sniper] to win."
The 9-year-old said there wasn't much schooling going on - especially not after the code red drew all students into the gym. "After lunch we just played games. We were throwing the ball. Then they said 'Sit down,' just in case somebody was out there," he said.