My son is in Y5 at an easy going school. It has been an advantage as they are not so SATs obsessed and so he had sometimes been given the opportunity to pursue his own, outside of NC, interests, although I do wish this happened more often.
Unfortunately, being a laid back school, they have been pushed to improve their SATs results fast, and so I think the school is rapidly becoming less laid back, which is not of benefit to my son. He has already been assessed as achieving 5As in all SATs areas and has not, and will not be until the end of next year, assessed beyond this.
The school has a high number of SEN and some locally don't send their children to this school as they are "too bright". We have been more than happy (most of the time) and our DCs have been able to mix much more socially than they would at other schools - a definite advantage for us. School is, afterall, about so much more than academic achievement!
The other schools locally which appear to do better academically (based on SATs results) have a very straightjacketed approach and parents of bright children often complain that all the children at the top end are 'kept together'. Also parents whose children are at these schools often complain that they are not listened to and that 'teacher knows best' whereas we've always been able to communicate with our school and rarely felt judged as 'pushy'.
Once they reach secondary school, they all seem to mix in from all the local schools, and those with more academic ability are identified quite quickly, irrespective of their primary school experience.
So, for us, Laid back has definitely been a good thing.