It is not actually about the accuracy of the exam. To let you know, to get admission to one of the Grammar Schools of England, Eleven Plus Examination is one of the eligibility criteria. So, there is no other choice if you want to prepare your child for Grammar School. Also, Eleven Plus Examination is a good way to choose good students from middle-class backgrounds. It is supposed to select the most academically able pupils irrespective of their economic status.