Am I being really thick here ( please don't all shout at once you'll deafen me 
) but what on / in earth is the point of bringing them home 
School children ~ being filthy little beasts frequently "come home" with worms. These are not 25 foot long tape worms but are passed from child to child by poor toilet hygiene. They reside just inside the anus, are a couple of millimetres in length and are never normally seen, they are white in colour. The first signs are usually that the child spends a lot of time scratching its bottom. Sometimes but not always, if you are very quick and willing to look, you can see them in the child's stools. The worms abhor light and as soon as the child drops it's underwear they retreat up into the anus. Dark pants can often be whipped down and examined in the hopes of proving an infestation. Usual treatment is a course of tablets over several days or even weeks to ensure that all the worms and their later hatching eggs are removed. The infection usually spreads quite quickly through a school. Washing of hands and frequent applications of ointment to sooth the itch are recommended. They are BTW Thread Worms.
We have been down this route several times ~ another good reason for home education.
Use Detol or something similar to clean the toilet seat at home everytime it is used and make sure every one washes their hands EVERY TIME preferably with a hospital type handwash.
PS How do you know The Boy has them Nick and why would you think (other than as a result of a fevered imagination) that you will have caught them from him already? Mrs S#2 and I have never caught them despite both boys having "Brought them home" on several occasions
