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.