We also know that many parents don't stick to that rule, much to the annoyance of teaching staff and those parents who fear their kids may now go down with the latest bug.
It's easy to be judgmental but, if parents work, it may come down to a straight choice between the health of their child and keeping their job.
Part time jobs, in particular, are difficult to come by and I know from my experience in the Legal Sector that part time positions are often created simply to be seen as adhering to "good" HR practice and in order to create roles for female employees returning from maternity leave!
The job may be part time, but the workload certainly isn't. 5 days work is cantilevered into 3 and woe betide you if you have to leave early to pick up a poorly child. You'll be equally unpopular with your bosses and the employees who have to pick up the slack in your absence.
If there is a tender document to submit or a presentation to give, you'd have to be very brave indeed to miss it. Come appraisal and pay-review time, the discussion will be about whether you are a 'team player'. Law firms are very fond of 'team players', despite having a hierarchy which is anything but flat.
This is without taking into account the cost and scarcity of good childcare. Our local childminders all seem to be oversubscribed and are followed into the playground by ever increasing numbers of children.
Breakfast clubs and after school clubs are thriving. In fact, so popular are they in Caitlin and Ieuan's school that the playground is often comparatively deserted in the mornings, with the children outside looking enviously at the children safe and warm within.
So when should you keep your child off school?
Be aware that the Government is quite clear that children should only miss school if they are too ill to attend or they have advance permission from the school - otherwise a fine may be payable.
If your kids are showing clear symptoms then it's a no-brainer but what do you do if they are a bit 'under the weather'?
These are the illnesses the NHS say merit keeping your child at home depending on their severity:-
Cough and Cold * Raised Temperature * Rash
Headache * Vomiting & Diarrhoea * Sore throat * Chickenpox
But what do you do when they have had a rotten night's sleep? Ieuan, for example went through a phase where he suffered from growing pains and often woke up in the early hours clutching his legs. But he was not ill.
If we let our children stay home for every cough and sniffle, what will happen when they really have to turn up and perform?
But when your kids awake bleary eyed, tired and weepy, complaining of head, ear or tummy aches, it takes a very hard mother not to want to scoop them up and put them back in bed.
Some of my fondest memories when ill are of being tucked up in bed by my mum, being fed tea and hot buttered toast, and listening to the radio. There is nothing like a bit of parental attention and love to aid a speedy recovery.
As a stay at home mum, that is a luxury I can offer my kids. But I think it's a shame that, as a society, we have got ourselves into a position where poorly kids have to be sent to school so that parents can keep a roof over their head.
I guess all we can do is make sure we practise good nutrition and take care of the family's health in order to stave off as many of these horrid bugs as possible.