If the storm that swooped through Washington early Tuesday was an early test of winter, by many accounts several of the region’s school systems failed.

Teen drivers crashed on the way to classes. School parking lots turned into gridlock, leaving parents seething. School buses fought slick roads, often unsuccessfully, with many school ­systems reporting crashes.

All the result of the decision to leave many of the Washington ­region’s school systems open on regular schedules Tuesday.

Jaha Knight, a junior at Tuscarora High, said her bus was 30 minutes late and took more than an hour to get to the Loudoun school, four times a normal trip.

“He was going really, really slow because he couldn’t see and the roads were really slippery,” she said. At school, she said, scores of her classmates were absent. Her Spanish class, normally crammed with more than 30 students, had just nine.

See how much snowfall has hit the region.

At least two serious incidents appeared related to students trying to make it to school, both in Anne Arundel County, Md., where a 17-year-old student was critically injured in a car crash and a ­15-year-old girl slipped crossing a street and was struck by a car that was unable to stop.

Bob Mosier, spokesman for Anne Arundel schools, said the decision to stay open was based on forecasts that showed a “dusting” of snow for the county. When snowfall started outpacing the forecast, officials contemplated a two-hour delay. They decided against it because they worried it would put young drivers on the road in the middle of rush hour with worsening road conditions.

“In hindsight, would we have done it differently? Yes, we would have,” Mosier said.

More than 60 percent of the region’s students — nearly half a million — had a normal school day on Tuesday, with most major Northern Virginia school districts opening on time along with D.C. public schools and almost all D.C. charter schools.

Montgomery and Prince George’s county schools made the decision to close. Dana Tofig, a Montgomery schools spokesman, said the district at first opted for a two-hour delay then closed completely as the snow picked up: “We got hit harder than anticipated, and the roads just weren’t clear enough to run the buses.”

The decision to open or close schools on a borderline day is likely to draw criticism. Last winter, parents expressed frustration over officials shuttering schools because of snow storms and cold weather, demonstrating the delicate balance officials must strike.

Arlington, Loudoun, Prince William and Fairfax county school systems apologized to parents Tuesday for the decision to keep schools open, citing weather that took them by surprise. Fairfax, Prince William, Loudoun and Arlington had already announced a two-hour ­delay for Wednesday classes as of Tuesday night.

The D.C. region woke up to a snowy Tuesday morning with accumulation hampering commutes and delaying school openings across the area. (The Washington Post)

Loudoun schools spokesman Wayde Byard said officials had to make a call at 4:30 a.m., when only one to two inches of snow was forecast to fall. By the time the forecast shifted, Byard said it was too late to backtrack. “We got caught in a change of forecast at the last minute,” Byard said.

Fairfax schools Superintendent Karen Garza also apologized for the difficulties the weather created. “It is clear that our decision to keep schools open today was the wrong call given the intensity of this weather system,” Garza said.

Virginia Del. Mark L. Keam (D), whose district includes Fairfax and whose 13-year-old son and 11-year-old daughter are students there, criticized the decision to stay open and the lack of communication about it.

“It’s not like they didn’t know this was going to happen,” Keam said. “It makes you scratch your head and wonder why were they so inept about this today?”

Many parents in the District said commutes to school took longer than usual due to messy roads, slippery sidewalks, and delayed or canceled Metrobuses. Only about one quarter of students attend their neighborhood schools; the rest head to school on their own.

Karen Zacarias said it normally takes 11 minutes to drive her two daughters from their home in Mount Pleasant to John Eaton ­Elementary School. Tuesday, the trip took an hour, and it was scary.

“There were so many cars spinning,” Zacarias said.

The decision to open D.C. schools and government offices was the first bad-weather test for the new mayor, Muriel E. Bowser, who drew fire for what critics said was a sluggish response.

Bowser said at a news conference that she spoke to Schools Chancellor Kaya Henderson early Tuesday. “Our schools were ready and open to receive the children with heat, teachers and the instruction and food service all available to them,” Bowser said.

Aaron C. Davis and Donna St. George contributed to this report.