Christine Gilbert, chief executive of Ofsted and chief schools inspector, said: "We found that schools are identifying pupils as having special educational needs when they just need better teaching and pastoral support.
"If they had been identified better in the first place, their needs wouldn't be so acute later on. More attention needs to be given to identification."
She added that there was a "poor evaluation at all sorts of levels of pupils' needs".
"With over one in five children of school age in England identified as having special educational needs, it is vitally important that both the way they are identified and the support they receive work in the best interests of the children involved.
"Higher expectations of all chilren, and better teaching and learning, would lead to fewer children being identified as having special educational needs."