when to keep kid home from school ?

The marketing company I work for is doing a campaign for Triaminic and their partnership with the National Association of School Nurses to create Sick Day Guidelines.

The Sick Day Guidelines aim to provide parents with the key signs that they should consider keeping their child home from school. They'll be available as a refrigerator magnet and will be handed out by school nurses across the country.

A lot of the guidelines I already follow, but it's a nice resource to have. What symptoms warrant you to keep your kids home from school? I know fever and throwing up are two big ones, but what about cold symptoms?