(1) In the face of an academic study, he replies with his own personal experience of school and growing up, from which – naturally – wider conclusions can be safely drawn.
(2) He ignores the fact that selection implies rejection: for every grammar school, there are two secondary moderns. Given “the reality of differential access to the educational opportunities grammar schools provide”, he suggests:
The antidote is, of course, to build more schools of this type, and, thereby, to restore to all today's youngsters the same advantages that I enjoyed - free - 50 years ago.
Yes, let’s have more selective schools. Then “all” children will be able to go to them.