Federal safety officials say they favor seat belts, but don’t propose a federal mandate. Last time the feds considered one, they came to a surprising conclusion: It might get more kids killed. That’s because buses with seat belts are more expensive. So districts might cut back on busing— which, even without seatbelts, is the safest way to get kids from A to B. The feds estimated 10 or more additional school kids could die every year.