I thought it was one exam for all schools but does it mean QM take the top percentile, then WGHS & so on?
No, it doesn't really work like that. Each school has an allocated PAN, published admission number. The PAN is commonly referred to the number of pupils in each year group that the admission authority has agreed will be admitted without causing problems for the school.
My understanding is that current PAN for WHGH is 145 and 120 for QMGH. Schools generally tend to offer 10 to 20% over the initial PAN figure as they know a lot of these offers will opt out and prefer a different school.
If they can't fill their PAN using the above offers, then they start picking candidates from the waiting list.
Coming back to your question, QMHS don't necessarily take higher percentiles. The last score admitted to any particular school really comes down to the number of parents putting that school down as first preference on local authority admissions form. You will find the most highly rated grammar schools to have a much higher cut-off, unless their PAN is higher than other schools.
To be honest 300 does seem a bit low for WHGH. But if they are advising you to put it down then there is nothing to lose. You will find that a score of 300 is 50th percentile, which would mean half of the all children taking the test scored above 300. For e.g. If 1000 children took the WHGH test, 500 would have scored above.
Hope that helps!
EDIT - I would like to add that WHGH have 25 more places as compared to QM. Hence, it's logical for their last cut-off to be lower(considering both schools were equally popular). I would guess that an extra 25 places would reduce the cut-off by approx 5 points. Could someone confirm if my PAN numbers for both schools are correct?
Sorry crossed with few posts