League tables are what you may find in a newspaper; they have already been ranked and are usually country-wide. Performance tables contain the underlying data; can be filtered and ranked using your own requirements, enabling you to retrieve data based on the location you’re interested in.
‘Top 100 Schools’, or similar, are fairly meaningless to a significant majority of families. Additionally, the measure used to rank the table is often flawed in one way or another.
Let’s take the Telegraph’s 2015 GCSE table, as an example, but this may also apply to other tables of this type.
The measure used is the Percentage of pupils obtaining at least five A*-C grades (or equivalent) including English and Maths (a standard one for GCSEs), and then by the GCSE Average Point Score per pupil.
So, the initial problem is the first measure used. A number of Independent Schools enter their pupils for the iGCSE exam (International version of the GSCE developed by Cambridge University), but some versions of these are not included in the Government’s official data; therefore those schools can record 0% in the first measure.
One of the top schools in the country is Westminster School in London, but it doesn’t appear in the table at all. Below are the relevant figures for that school (from the Gov data, here), showing that, on average, the pupils have 6.1 (GCSE or equivalents) entries. Obviously they are actually taking more than 6 GCSEs each! By comparison, The Blue Coat School (top of the above table) has 13.1 entries per pupil. If the Westminster School offers the non-accredited GSCE in only some subjects (particularly not the Core subjects) then they are not going to record a figure in the measure used by the table in question, i.e. they won’t qualify for inclusion.
Now let’s take a look at the equivalent A-level table.
This table is ranked according to the Average Point Score per pupil and then by the Average Point Score per entry.
The former is the total point score the pupil achieves across all entries. Therefore, the table favours schools which ask their pupils to enter an above average number of A-levels or equivalents (maybe 5). A significant number of schools at the top of the table offer the International Baccalaureate Diploma instead of A-levels. This is a more all-round qualification and is made up of more ‘entries’ than the average A-level pupil would take, skewing the results in their favour.
Personally, in this case, the second measure should be used to rank the table. Average Point Score (APS) per entry is a truer reflection of the pupil’s achievement, i.e. quality over quantity.
The range of values in this measure shows the extent of the problem. An APS value of 255 is equivalent to a grade A, which a lot of schools in the table achieve, however some schools show a value around 200 which, on average, is a grade C. This doesn’t seem like a Top 100 school to me.
Take this example, pupil A scores an average of 250 for 4 exams, giving a total APS of 1000. Pupil B scores an average of 220 for 5 exams giving a total APS of 1100. Pupil A has 4 grade B’s but 100 less total APS, pupil B has 5 grade C’s – which is better?!
In both tables there is, either, missing data or a misleading ranking measure. When looking at these types of tables pay attention to the measures used to create the ranking.
These contain the full performance data and can be used to derive a measure, or measures, which are suitable for your requirements. This will be the subject of the next post. We need to find measures which are meaningful. If you are just looking in the State sector then it is fairly easy to do. However, if you are looking in the Independent sector and especially if looking in both, then it is harder to achieve, particularly creating a measure where State and Independent performance can be compared.
For info, the relationship between A-level grades and APS values can be found here, in Table 1.
In 2010 the Government allowed UK State schools to offer the iGCSE qualification. ‘Certificate’ accredited versions of the iGCSE were created so that the State schools could gain funding for them. Later, as you can see from the 2013 entry above the non-accredited versions (offer by a lot of Independent schools) were removed from the data.
To make matters worse, the Government is reforming the GCSE qualifications, starting with English and Maths for GCSE courses which commenced in September 2015. In 2017, when the first reformed exam results are known, any iGCSE version will be excluded from the Performance tables.
From the Gov:
No unreformed GCSEs in English and Mathematics or other academic qualifications such as IGCSEs will count in the tables (for 2017).
The point of all this is that a common measure needs to be found to accurately compare all school types at GCSE level (more on this later).