Look, I know this is the internet, so rational argument is unwelcome. But by any rational standard, the omission of Grammar from the 1st XV competition is sensible. No-one benefits from risking serious injury whilst being defeated 112-0. The schools have a duty of care to their students - if someone had been seriously injured while playing against an opponent forty kilos heavier, it would have been no defence that tradition required it.
Tradition is often a good thing. It can also be a straitjacket. If tradition mandates the continuation of an uneven and dangerous competition, it should be abandoned. It surprises me how people who love to bang on about "tradition" turn out to know very little history. In the early days of Rugby, only goals counted in the score (a "try" was so called because you got to try to kick a goal - but if you missed, you scored no points). Well, that was an early Rugby tradition. Anyone want to go back to it? Well, how about hacking? In the early days of Rugby, the laws allowed hacking, which was defined as kicking the legs of the ball-carrier between the knee and the ankle. Anyone want that tradition back?
Traditions change when things need to be improved. That is what has happened here.
And, by the way, you'd be surprised how quickly new traditions begin. These days you hear people talk about the "traditional" MCG Boxing Day cricket Test. Well, that tradition is just over twenty years old (it replaced the traditional NSw-Victoria Sheffield Shield game - which almost no-one cares about, and no-one seems to miss).
There are two concerns about the change - that good Grammar boys may miss GPS selection, and (my own) about the suitability of the home-and-away format. The first is, I think, a non-issue. If a genuinely talented Rugby player emerges form Grammar, I don't doubt pragmatic ways can be found for him to progress. There are so many avenues available now that there is scope for anyone with talent and ambition to find a path forward. The second is my own concern, though not too many people seem to share it. The home-and-away format in the Associated Schools competition has turned the competition into a real grind, and in the few years it has been running, it has never once produced a close competition, the winner having been close to unbeatable at the halfway point. And it reduces, even eliminates, the prospect of meaningful inter-association games (such as Scots/Cranbrook, Knox/Waverley, Newington/Trinity), which I think is a shame.