this phrase can be linked to the following part of Neverstreaming: Preventing Learning Disabilities, written by psychologist robert e. slavin:

Once upon a time, there was a town whose playground was at the edge of a cliff. Every so often a child would fall off the cliff. Finally, the town council decided that something should be done about the serious injuries to children. After much discussion, however, the council was deadlocked. Some council members wanted to put a fence at the top of the cliff, but others wanted to put an ambulance at the bottom. In this parable, the idea of putting an ambulance at the bottom of the cliff clearly is foolish on many levels. Waiting for children to be injured and only then providing them with help is cruel and inhuman if the damage can be prevented. Further, it is needlessly expensive; an ambulance costs far more than a fence.

slavin has authored or co-authored more than 200 articles and 15 books about learning problems at a young age.