A lap-only belt is not safe for anyone at any time. It is especially unsafe for a small child, because the belt is likely to ride high on the belly. In a crash, thousands of pounds of force will be directed into the soft tissues of the abdomen. This is "seatbelt syndrome" and it can be fatal. Riding in a lap-only belt is not an option that should even be on the table here.
OMG, it really sounds unsafe... but WHAT DO PEOPLE DO? Do you all have your children in harnessed seats on school busses, or just make the commitment to drive them to/fro school daily in your own car? Until they're how old? From what you described, it's not safe for a 15-year-old! The E-Z-ON Cam and the SafeGuard Star sound great but yes, they're expensive! I'm going to consider them but I don't see most parents and/or most schools, even private schools, being wiling to spend the extra dough on them.
I don't want to be that weird mom who "over-protects" her child... you know -- the poor kid that gets covered head-to-toe w/ SPF 50 wear on every school field trip while all the other kids are running free... I think most school busses are lap-belt only, right? If I think he might rebel at sitting in a harnessed seat now at age 4.5, wait 'til he's 6, or 8, or 12! At least the E-Z-ON Cam is just extra belting w/ no seats, maybe that would be a good choice for now. But once he's in public school next year, would they even allow me to keep that on the bus so that he can use it daily? Sometimes they're on different busses morning and afternoon, so I'd have to buy two!
What do you all do for your own kids? It sounds like a lot to do that most people don't do at all... Should I just shrug and let him on the bus just like all the other kids his age? I remember another thread on this forum about how safe school busses are and how rarely they get into accidents...