My son sat Olaves this year (I already have a son in year
and the cut off was 149 (certainly higher than the last 2 years). My son missed out by 3 points on 146 but is number 28 on the waiting list. I know that in my eldest son's year 2007 the cut off was around 130 but the waiting list went down to about 128 (as I know one boy in my son's class who got in and he was number 26 on the waiting list). He got in around May time.
Last year's cut off was lower than this year but was higher than 128 I think it was around 140 but am not sure.
You really cannot tell what the cut off is going to be as each year is different. What I can tell you is that if there is a tie on scores they take the maths into account.