Revise the following paragraph, omitting wordiness, correcting any grammar and punctuation problems and putting the main focus at the beginning:

For over 20 years, teachers and parents have expressed concern over those children whose parents stop their cars in the centre of the parking lot and send their children unaccompanied across the parking lot towards the playground. While one car stops even for a minute, five or six others may be forced to wait in the parking lot. Parents anxious to get to work then open their doors and release their passengers to save time when the way is clear and they are able to proceed. Children dart between the waiting cars unaware of the dangers this action entails. Because this occurs not in a designated driveway but in the school parking lot, there is the added hazard of drivers leaving the parking lot. The longevity of this problem is evidence that the above -mentioned carpool habits are ingrained in the drivers who bring children to the school. Regulations and policies have little effects as enforcement is difficult for the one teacher who is on outside duty before school. Additionally a question of immediate convenience (dropping off the children mid out) often overrides the question of safety.