one of the areas our confederation of 11 schools looked at was social exclusion...we live in an area of high social deprivation (on 40th centile) on the border and in the same area as schools on the 99th centile. Ie we are a poor area in a rich borough. The issue that concerned us was that academies get to select their own admission criteria. Given the choice, who would not jump quickly and select an area that is a) wealthy and b) has a high proportion of intelligent families? Of course your results would be great, your parents supportive financially - whats not to like?
The concern was that children from poor areas would all end up in the same schools, creating "ghetto" schools of children - having to pick up children from potentially high need areas, and vulnerable families like travellers, children with SEN, children where there are safeguarding concerns...
(our school had 50+ % children at end KS1 in school action or School action plus. Average 30% every year).
We already see this in our area - more well to do parents drive their children 4 miles to another infants rather than use ours, because of the high number of SEN kids. Plus they want to get little Tarquin into school X, which already has an admission policy that favours children from certain social classes schools.
So its the very worst form of social engineering.
It was felt, in our federation, that we would be forced by weight of numbers to go academy at some point - after all, who wants to be left with a catchment area of 4 rough council estates, spread over two districts? However, only one primary has, as yet, decided to go for academy status, and they cannot, as they got a satisfactory ofsted (and you need an outstanding or to be a failing school to get academy status.)
There were also concerns about finances....recently the council offered internet services at a HUGE premium, most schools in the area accepted the term! We opted out, and made a cost saving of several thousands. Likewise, building work - council offered their contractors at £70k; we opted out and got work done for £30k.
Where schools go academy, especially small infants like ours, we lose the head teacher autonomy and end up going down the path of least resistance (which may not be the most economical).