Unless my maths has gone the same way as most of my joints, I don't think it does. As an example, we have 10 people of whom 9 have 10 GCSEs & 1 person has 1 GCSE.
The average (mean) is 9.1 GCSEs so only 1 person is below average, not 5.
The median is 5.5 so, again, 1 person is below the median, not 5.