Do pupils make most progress in comprehensives or grammar schools?
The jury is still out after new rankings were published this week, considering for the first time how youngsters' results improve between the ages of 11 and 16.
Not a single grammar school features in the top 10 secondaries ranked according to this "value-added" measure, which compares pupils' GCSE results with the scores they achieved in their key stage 2 tests at 11.
Eight of the top-performing schools are comprehensives, while two are state special schools. The top-ranked grammar, Woodford county high, is placed 11th overall.
However, looking slightly further down the list, the picture changes.
Grammar schools fill 38 out of the top 100 spots, and 98 of the top 300.
These figures suggest grammars, which make up just 166 of England's 3,700 secondaries, are disproportionately represented near the top of the tables.
The new "value-added" measure has been introduced by ministers in response to heads' concerns that traditional league tables disadvantage schools in deprived areas and non-selective secondaries.
But this year's results do little to shed light on the advantages or otherwise of selection. Confusion also reigned last year, when there were separate measures of pupils' progress from 11 to 14, where grammars did better, and between 14 and 16, which comprehensives dominated.
Opponents of selection also point out any analysis of the success of selective schools must include secondary moderns, who took only two of the top 100 places.