Elphaba is right for out of catchment boys ABGS is effectively "super selective" and don't be fooled by a score of between 353-356 this is a very high score due to the way raw scores are standardised againt it's own cohort IMO (due the "bell shaped" distribution of the standardisation the difference between 360- and 421 is only a few raw marks because only a few children are "at" this extreme end of the steepest-negative gradient- part of the curve- best mathematically descibed by a logarithmic scale-',,,small changes at extremeties have a "butter- fly effect") translates to about the top 10% of the national cohort, in other words ,a small difference in raw scores has massive (disappropriate) difference in standardised score at this extreme ability range (however DC form local prep schools distort natural ability by over prepping and tutoring on top , hope they can cope in classes over >30!!)
hope that makes sense!!
and for UGS to get into the top "20" your child needs to be within the top 5% nationally!! tough ask for any child (potentially Oxbridge/Medical School material)
I would say when your child is doing the last 4 practice papers from GL (the first 4 papers used for familiarisation), needs to be scoring >95% ave in all papers!! to get > 400 on national standardisation and >360 on the aggs/abgs exam
but don't worry most kids do not need to get any where near these almost perfect raw marks (95%+ on practice/mock GL practice papers) for entry to GS but more relevent to out of catchment children.
BTW not evidence based only my opinion , based on my own analysis/experience and I am more often than not ,wrong
btw I no "axe to grind" my DD is not going to any GS