Early on a weekday morning, your child steps onto a school bus. The yellow doors shut, and that waving hand disappears down the street -- with a total stranger behind the wheel. It's hard not to feel anxious at that moment, especially in light of the incident earlier this year when a bus driver with a loaded rifle took 13 kids on a six-hour unexpected ride from Pennsylvania to a Washington, DC, suburb. No one was hurt, but this episode raised questions about how schools screen drivers.

About half of children in the U.S. ride buses to school. States or individual school districts can decide whether to check for a criminal history of anyone getting a commercial driver's license, but school bus drivers are also subject to a federal mandate that permits, but does not require, random testing for drug and alcohol offenses. Criminal background checks are required in every state except Iowa, Montana, North Carolina, North Dakota, and Virginia -- but there are different standards, for example, on how far back in the record to look, says the National Association for Pupil Transportation in Albany, NY. In any case, even the best screenings can offer only partial reassurance. Taking these steps can help ensure that your child's driver is one who deserves your trust.

Get details on your driver. For privacy reasons, school districts usually won't reveal information from an individual driver's personnel file -- including whether other parents have filed complaints against him, according to the Dover, DE-based National Association of State Directors of Pupil Transportation Services. At least, that will be the official stance.

But if you approach a driver's supervisor as someone who, like you, wants what's best for kids, he may let you know privately whether a driver has been a problem, says Jim Ellis, a training-curriculum specialist at the Pupil Transportation Safety Institute in Syracuse. Ask what happens to drivers who have complaints lodged against them. Also try to find out the previous neighborhood assignments of the driver on your child's route. Then talk to parents in those areas about their impressions of the driver.

Find out the basics. Ask your school district's director of transportation to explain how local drivers are screened. If you live in one of the five states that don't require criminal background checks, lobby your school board to make them mandatory.

Report concerns. Before the Pennsylvania case, no driver had ever hijacked a school bus (though, in a few isolated cases, parents have). More common problems are drivers who seem mean to kids or who upset children by yelling. If you have concerns about the way a driver behaves with your or any child, try speaking with him first (ask at the bus stop how to get in touch for a private conversation). If that doesn't resolve the problem to your satisfaction, bring your concern to the school's director of transportation -- or the administration or school board. "It's important to work your way up the chain," says Ellis. "Supervisors don't want something bad to happen to a child on their watch."

Keep problems in perspective. The Pennsylvania incident was a rarity, and the fact is that it's unlikely your child will come to harm on a school bus. "The safety record on school buses is exemplary," says Ellis, citing nine deaths nationwide last year. "Each of those cases is tragic," says Ellis, "but school buses are still one of the safest forms of transportation in the United States."