Letters were sent to all schools near Woodkirk Quarry in Tingley before they broke up for the summer break warning of the dangers of playing in quarries.
PC Kevin Oates of West Yorkshire Police said: "Children are naturally attracted to large open spaces like these.
"However, some are not aware of the risks that lurk within the quarry."
Some of the dangers include submerged machinery, steelwork and barbed wire, sewage in the water, quicksand-like sludge and pockets of deep, cold water.
Stephen Reeves, the general manager of Woodkirk Stone, said: "We would also like to remind the children that the quarry is private property and is monitored by a camera system.
"If you enter the quarry then you are posing a risk to yourself and others, and we shall not hesitate to involve the police if appropriate."
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