The Times Editorial: It's every parent's nightmare - one's teenage son or daughter develops a drinking habit and goes off the rails. Too often too many of us blithely drop off our children at ''supervised'' parties, at their friends' homes or at supposedly safe shopping malls, without checking what they really get up to.

Elsewhere in the paper we carry a report about the head prefect of a top private school who was stripped of his title after he was caught driving under the influence of alcohol.

There is sufficient anecdotal evidence suggesting that under-age drinking is becoming a big problem in South Africa, and harsh measures are required to stamp it out.

For this reason the announcement that Gauteng is finalising legislation to deal more harshly with alcohol abuse by teenagers is welcomed.

According to Kenneth Mapengo, chief director of the Gauteng Liquor Board, the aim of the draft amended legislation is to ensure that ''institutions such as schools and places of worship'' are protected. To this end, law-enforcement authorities will be given more powers to deal with liquor outlets that break the law by selling alcohol to children, and more severe penalties will be imposed.

Earlier this year, provincial officials vowed to clamp down on shebeens and other liquor sellers close to schools - particularly the province's 20 worst-performing schools - because they are believed to be the main reason for the declining matric pass rate.

A proposal to prohibit liquor sales after midnight at pubs, shebeens and nightclubs is also under consideration.

Though the envisaged changes, along with the eventual regulation of all shebeens, will go some way to protecting our children from exposure to alcohol, they are no substitute for effective supervision by parents.