It started with the Italian economist Vilfredo Pareto in the early 20th century and was developed in the 1940s by Dr Joseph Juran. The principle holds good across a huge range of activity. But does the ratio work in school? Well, let’s see. Are any of the following true for you? (Don’t be too hung up on the exact percentages - it’s a principle, not a rigid rule):

* 80 per cent of disciplinary problems are caused by 20 per cent of the pupils.

* 80 per cent of your school’s success is down to 20 per cent of the staff.

* 80 per cent of a lesson’s aims are achieved in 20 per cent of the lesson.

* 80 per cent of your staff absence is accounted for by 20 per cent of people.

* 80 per cent of the photocopier bill is down to 20 per cent of the users.

* 80 per cent of the staffroom biscuits are eaten by 20 per cent of the staff.

And so on. You now want to make the principle work for you. Be careful, though, because it can be misunderstood. Some take it to say, for example, that you should spend your management time and effort on the 20 per cent who produce the goods. Seems plausible, but as another management guru, F John Reh, writes on his website (http:about.com): “The theory is flawed because it overlooks the fact that 80 per cent of your time should be spent doing what is really important. Helping the good become better is a better use of your time than helping the great become terrific.”

Here’s a rule-of-thumb test to find which side of the divide you are on (it comes from the American Academy of Family Physicians: www.aafp.org). You are swimming against the tide with the 80 per centers when you:

* are working on tasks that other people want you to, but you have no investment in them.

* are frequently working on tasks that are labelled “urgent”.

* are spending time on tasks you are not usually good at doing.

* are taking longer than you expected.

* find yourself complaining all the time.

Did you tick any of those? What, all of them? Get away.