School boards hire outside companies to handle their transportation needs for numerous reasons, including wanting to cut administrative challenges that come with running their own busing system, says
the National School Transportation Association, an advocacy group for bus contractors.
These companies hire their own drivers and operate and maintain the buses they drive.
Here is a look at the outsourcing of school bus services in the United States, and at Illinois-based Durham School Services.
School Bus Fleet, a trade publication for school transportation officials, last year published bus statistics from all 50 states from the 2012-2013 school year. Out of about 472,000 school buses nationwide, 34.7% were owned by contractors, and the rest were owned by school boards or states, the magazine reported
That's up from 2007-08, when 25.6% of the nation's school buses were owned by contractors, according to the magazine
How many students does Durham serve?
Durham says it gives rides to more than 1 million students every day in 32 states, using more than 16,300 buses.
Durham is a subsidiary of National Express LLC, which says it is the second-largest provider of outsourced school bus services in North America. Durham runs the vast majority of National Express' school bus operations.
How does Durham fit into the overall picture?
About 26 million students ride school buses -- outsourced or not -- in the United States, says the American School Bus Council
, a coalition that includes public and private transportation providers.
The largest outsourcing company, First Student Inc
., says it transports about 6 million students
per day, using 47,000 buses in 39 states and seven Canadian provinces.
What training do contract drivers receive?
States have varying rules on screening, training and evaluating school bus drivers.
Durham says it meets the rules in every state in which it operates. It says that its drivers, before being hired, must pass a criminal background check, an inspection of his or her driving record and a drug screening.
Hired drivers get specialized classroom and behind-the-wheel training, and are subject to an annual driving evaluation, the company says.
What is Durham's safety record?
Durham has a satisfactory safety rating from the Federal Motor Carrier Safety Administration
The bus company in 2007 was given a "conditional safety rating" from the Federal Motor Carrier Safety Administration. It was later upgraded to "satisfactory" after the unspecified problems were resolved, said Christopher Hart, chairman of the National Transportation Safety Board. A website lists the most recent satisfactory rating date as July 31, 2015.
In the last two years, the company's buses have been involved in 346 crashes before Monday, resulting in four deaths and injuries to about 275 people, the FMCSA says.
The FMCSA's information makes no comment on the degree to which the buses were involved in the crashes, who was at fault, or whether the dead or injured were on the buses.
The fatal crashes happened in Memphis, Tennessee, on September 7 (one dead
); St. Louis, Missouri, on October 5, 2015 (one dead
); and Waterbury, Connecticut, on February 17, 2015 (two dead
None of those who died were passengers or drivers of the buses, CNN affiliates reported at the time.
Compare that with the record of the larger contractor, First Student Inc., which the FMCSA also gives a satisfactory safety rating.
First Student buses were involved in 886 crashes in the last two years, resulting in six deaths and injuries to about 660 people, according to the FMCSA
As for Durham drivers, 53 "unsafe driving" violations were reported in the last two years, most of which (30) involved failing to use a seat belt, the administration said. Other of the more frequent violations were failing to obey a traffic control device (eight), using a mobile phone while operating (seven) and following too close (three).
First Student had 44 unsafe driving violations in the same period, including 17 for not wearing seat belts, nine for speeding, and four for failing to obey a traffic control device, the FMCSA says.
What has Durham said about Monday's wreck?
In a YouTube statement
, Durham School Services CEO David Duke said that, as a father and grandfather, he has struggled to "get his mind around what happened" and that he was filled with pain.
"I can't fathom the anguish of the parents whose children were involved in this horrific accident and it involved one of my company's buses," he said.
"Nothing that I can say can take away the pain and the grief for these families. What I can say is that I'm deeply sorry for the children that were taken from their families with so much life before them."
He said the company was cooperating with National Transportation Safety Board and local investigators.
"My responsibility now is to look for answers -- answers about why this tragedy occurred and answers for how we can make sure that this never, ever happens again," he said.
"I don't want to compromise that investigation. I want to know what happened. I'm not able to elaborate on either the accident or the investigation ... . What I can do is promise that I'm determined, that we're determined, to find out what happened. And that we will offer any support that we can to the families."