GMC 1997 Savana Van Owner's Manual page 57

Larger Children
Children who have outgrown child restraints should
wear the vehicle's safety belts.
If you have the choice, a child should sit next to a
window so the child can wear a lap-shoulder belt and
get the additional restraint a shoulder belt can provide.
Accident statistics show that children are safer if they
are restrained in the rear seat. But they need to use the
safety belts properly.
Children who aren't buckled up can be thrown out in
a crash.
Children who aren't buckled up can strike other
people who are.