In reality I suspect in junior schools teachers have had a lot for freedom to teach a more balanced curriculum over the past two years because they have not had to waste so much time preparing for pointless SATS tests. As a result many pupils will be going off to secondary school better prepared than in the past. In secondary schools more and more schools have moved towards teaching GCSE's over 3 years rather than 2 years so this provides plenty of scope to allow pupils to catch up without the need for extra lessons or individual tuition.
The pupils who have missed out the most are the pupils who have been doing their GCSE's and A Levels in the past couple of years but no new catch up funding is really going to help these groups now. These pupils will probably need extra assistance at university particularly in science courses because pupils have missed out on lots of practicals over the past couple of years.
At the end of the day Williamson has dug himself into this hole and hopefully he will get the axe in the next coiple of months.