The thing is, my understanding is that there are different 'flavours' of free schools.
As LAs cannot open new schools, some free schools are created where LA schools would previously have been - need identified by LA, sponsors sought in an orderly manner, schools established using sensible expertise from existing schools. These aren't 'real' free schools, in many ways - they are simply called free schools because they can't be called LA schools any more.
Others are extensions of existing academy trusts, for the same reasons.
Other free schools - I note there are some Steiner schools on the list - are former fee-paying schools that have used this route to become state funded.
Still others - of which this seems to be one - are the original 'parent led' model, where groups of parents of varying expertise get together and decide to start up a school.
I suspect that if you divided the grades up into these types, it would be very revealing. A bit like the 'academy' label which lumps converter academies (self selecting Good or Outstanding schools, originally well-bribed though no longer) with forced / sponsored academies (usually failing schools) so that the average Ofsted grade for 'academies' as a group looks OK and the policy appears to be successful