http://www.guardian.co.uk/education/2010/sep/14/half-special-needs-children-misdiagnosed
For a start the headline is misleading. They aren't talking about the school actually diagnosing SN. Schools can't do that. They refer a child to outside agencies and if a diagnosis is deserved it will be given by them. The outcome of a diganosis or not is nothing to do with the school.
What the headline is actually talking about is schools "diagnosing" that children need to be put on a School Action plan.
Ofsted regard all children on School Action as having SEN, when actually a lot of them are NT. They just may need extra mentoring, coaching or counselling for example due to a trauma that has happened in their lives, due to their upbringing, due to being in care etc. They are saying this level of mentoring, coaching or counselling should come under pastoral care. Or the children may just be a bit behind the others or slow to progress and need some extra tuition.
What is actually at fault is not the schools but the system. They have to put these children on School Action so they can get schools mentors, counsellors, TAs for teaching small groups etc rather than have these children disrupting classrooms or get low self-esteem because they aren't progressing as well as they could with extra help.