You tell your victim that their shoe laces are undone, when they're not. If your victim looks down, they're an April Fool.
Other traditional tricks include sending someone to buy tins of striped paint or elbow grease. In 1998, many Americans fell for a story that Burger King had created a "Whopper" for left-handed consumers. Its ingredients had supposedly been rotated 180o.
The custom making April Fools of people dates back to 1582 when France adopted the Gregorian calendar and moved New Year's Day from March 25 to January 1 (see last week's Dates for Assembly column). The French traditionally celebrated the New Year for a week, with much feasting and drinking on the last day of the holiday, April 1. Many people refused to believe the change and were mocked as April Fools or, in French, poissons d'avril. They were named poissons (fish) probably because of the abundance of newly-hatched, easily caught fish in French rivers during early April.
To this day, French children fool their friends by sticking paper fish to their backs. When the victim discover the trick, everyone shouts "Poisson d'avril" - a fish on someone's back.
In Devon, the day became known as Tail-pipe Day because of the custom of pinning a note saying "Please kick me" to a person's back.
In Scotland, it is Gowkie Day ("Gowk" is a Scottish name for a cuckoo). A typical April Fool trick was to send someone "hunting the gowk" - that is, to send them on an impossible errand, such as to find hen's teeth. Customs like this may even date back to Roman times when people held a springtime festival called Hilaria (from which we derive the word hilarious). In contrast, we now often use emails to make April Fools of people, and these tricks can be harmless or malicious.
Discuss the difference between a fair and a cruel April Fools' joke. Look for broadcasts or newspaper articles - and news stories that are probably true but which strain credulity - of April Fool jokes. There are links to many April Fool sites at www.links4kids.co.ukaprilfool.htm
For a comprehensive French site (but with a less than perfect automatic translation), visit www.csdm.qc.carecit-adapt-scolCoffrepoissonAp-avril.htm