I’m sure that we all use spreadsheets to collate student data.  Some teachers will collect many pieces of data over a year.  How do you calculate an average mark?

I took some KS3 APP data (you can’t see it all here) and calculated the average in different ways.  As you can see the method of calculating an average can make a whole level of difference.  The longer the time you are measuring over, the more significant the difference is.

My preferred method is to average the five highest marks.  I aim to collect around 10 pieces of APP data over a year from a variety of activities.  You would expect pupils to make progress over a period of time, with the amount of progress proportional to the time span you measure over.  Are you doing pupils any favours if you take a simple mean average?

I’m not convinced that my method is best, but it allows students to have a few ‘off’ days without bringing down their average.  What method (and over what span of time) do you calculate an average?  What method works best for you and why?