A young girl running on grass
The young girl runs to join her classmates at the end of the recess period.
A young girl can run for reasons other than to join her classmates. A girl running is not necessarily running at the end of a recess period.
We do not know if the girl is running to join a classmate nor what time of day it took place. She may not be at recess.
A young girl doesn't necessarily run to join her classmates at the end of recess period.