I don't have any knowledge about this particular school, but I do know that these scores reflect how well year 6 children are taught to pass the SAT tests, not how good the school is at teaching literacy and numeracy.

My son is in year 6 at the school at the top of that table. From Christmas to May (when they sit the SATs) all the year 6 children are having an extra two hours of 'booster' classes per week, after normal school hours, focussing on raising their scores in the SATs. By contrast, my friend's son goes to a school where they don't do any prep for the SATs and get 'poor' SATs results, which would appear very low on this table, but it is still deemed by most of the parents to be a very good school indeed.

Lies, damn lies and statistics.