"Anyone who analyses 'won't' and 'capable of' as adverbs, 'a pair' and 'set of' as adjectives, or 'Sam's' as a possessive pronoun has no business to be preparing a resource on English grammar for teachers."Ha! This is the same teachers union which is busily shoving their perverse left-wing anti-human ideologies down your kid's throats. Maybe they should learn something about grammar before they teach it, and about life before they presume to interfere in the parent's job of morally educating their own children.
But what do they say in their defense:
ROFL! Now I see. Mistakes are just 'different perspectives', just like how little Timmy's assertion that 4+4=5 is another perspective that needs to be defended - at the expense of the other students who got it right, of mathematics, and of human progress generally.
"It's a totally different perspective and a totally different way of organising and thinking about language,"
(note my Oxford comma after "mathematics" haw haw)