When Erin Fish got a call from Seattle Public Schools this week notifying her that the bus carrying her 4-year-old to preschool had been in an accident, she’d already begun running through a list of worries. The call came late — 20 minutes after her neighbor, Kennedy Leavens, had already informed her.

Hearing the voice on the other end confirm that her son was OK brought little comfort. Declan has twice been diagnosed with brain cancer  — first when he was just four months shy of his second birthday. He’s undergone eight surgeries since.

When the caller told Fish that another bus would come to take Declan to school, Fish said she responded, “Absolutely not.” Even though the district wasn’t sure where the bus was at the time, she left work at REI’s headquarters in Kent, where she’d just arrived, to get Declan. Fish took the rest of the day off from work on Monday. Since her son began riding the bus last year, she said, it’s not usual for her to miss work.

She’d had a nagging feeling about the bus driver who was temporarily covering her son’s route that morning. She arrived an hour late, Fish said, and was driving erratically.

Though parents are reporting more consistent bus service in the last year, there have still been patches of hourslong delays since the start of school. Tracking them is difficult; the district’s web page showing delayed buses isn’t always up to date. But even the limited information on the site shows days where more than a dozen routes have been up to two hours late.

Recent data provided by Seattle Public Schools and its primary school-bus contractor, First Student, shows there are enough drivers to staff each of the district’s 353 routes. Even so, the data also shows that only 330 drivers have been driving a dedicated route. The district says the bargaining agreement between First Student and Teamsters Local 174, the drivers’ union, doesn’t require that drivers pick and stick to a particular route; they can choose to become a “cover driver” and fill in for unassigned or absent drivers instead.

“Unfortunately, routes without permanent drivers may experience delays,” said an emailed statement from the district.

This inconsistency hits kids with significant cognitive and physical disabilities and their families the hardest, for logistical and emotional reasons. Temporary drivers taking on a special-education routes are expected to adapt to both new geography and students with significant needs.

While the goal is to have the same cover driver until a position is filled, sometimes absences on other routes mean drivers get swapped around.

That was the case for Fish and her neighbor Leavens, whose sons are guaranteed door-to-door school-bus service from from Beacon Hill to their preschool at the University of Washington. The bus carrying their kids struck a car as it tried to merge onto Interstate 5, the mothers told The Seattle Times. Morning traffic meant the cars weren’t going very fast; pictures Leavens took from the shoulder of the freeway, where the bus pulled over, showed the other car with noticeable but not critical damage.

Leavens was also tipped off about the accident before the district called her. She called the preschool to make sure her son had arrived, and the school told her about the accident. She says the district didn’t contact her until an hour later.

Their sons, Declan and Ladd  — who is 3 — were the only kids on the bus. They both have developmental disabilities, and both find it hard to communicate. But even though Ladd has a speech delay, Leavens said, he’s been talking about the accident, calling it scary.

“It’s a big deal from a kid who doesn’t use a lot of language,” she said.

Both mothers said they noticed something was off about the driver, who has since been fired, according to the district. After showing up an hour late for their typical 8 a.m. pickup, they say, the driver drove erratically. Leavens said she saw the bus driver pull into a busy street, start to make a right turn, stop suddenly, then turn left. Fish said the driver drove past her and her son as they were waiting out in the street several times. Leavens confirmed that account.

Leavens, who works from home and was tipped off about the accident before the district called her, arrived at the scene of the crash first. She found the bus pulled over on the shoulder of the freeway by happenstance; the intersection she says the district had given her, Holgate Street and Columbian Way, doesn’t exist.

Leaving her 11-month-old daughter in the backseat, she got Declan and Ladd into the car and waited for Fish to arrive. The scene was emotional when she did.

The route now has a more regular cover driver, per the parents’ request. But it’s still unassigned.