Why play should come before grammar

Philip Pullman in The Guardian argues that children should learn to play with language before they are taught the formalities of grammar.

A word often flourished in this context by the common sense brigade is "basics". It's always seemed curious to me that commentators and journalists - people who write every day and who presumably know something about the practice of putting words on paper - should make such an elementary error as to think that spelling and punctuation and other such surface elements of language are "the basics". These, and deeper features of language such as grammar, are things you can correct at proof stage, at the very last minute, and we all do that very thing, every day. But how can something you can alter or correct at that late point possibly be basic? What's truly basic is something that has to be in place much earlier on: an attitude to the language, to work, to the world itself.