happened on the LA watch
As you know, the LA was powerless to intervene or make any changes between 2010 and 2015, until the LST agreed to hand them back, because they were under the governance of an academy chain over which the LA had no control and little influence. But the chain was underperforming.
Until 2010 the schools were under LA control but they were in suspended animation for two years leading up to academisation. The schools were always at a disadvantage since the link system worked against them, drawing pupils from the more middle class side of their catchment areas. Despite this, they maintained a fairly constant pattern of applications, stable leadership (especially Hampton) and local loyalty.
Who knows how quickly they might have improved had the link system been abolished earlier, and accessed rebuilding funds like Teddington, without having to turn into academies.