Why did the injury rates fall in the intervention schools
and rise in the nonintervention schools? Possible explanations
include changes in the physical environment, in exposure,
in supervision or in reporting. We believe that the
change in physical environment is the best explanation.
The physical environment improved in the intervention
schools, where injury rates dropped. It was possibly deteriorating
in nonintervention schools, where injury rates increased.
A reduction in injuries not recorded as being
“equipment related” is explained by the fact that the entire
outdoor environment was addressed in those schools undergoing
equipment removal and replacement. Additional
dangers such as fragmented asphalt, poorly drained and icy
areas, steep embankments and degraded borders were repaired
or safely landscaped during equipment replacement.