Yes and no. Also a growing trend amongst the schools for either getting the students repeating a year when a "sportsman" commences in the older age groups or putting them through year 11 and 12 over three years.
So that in their final year, the students are 18 and "hardened" athletes.
One school is known for actively getting their students to do only one subject and sometimes two in their final year (having elected to do year 12 over two years) and then pay the students to do groundsman work on their fields during the spare time across the day.
Another school is aligned to the NSW schooling system for the age the boys start at the school (being six months behind the QLD system) and they dominate the Open Age Groups year in, year out because the boys are on average six months older in Year 12 and have already played Open in the season before.
Look at many of the outstanding rugby players this year from some of the schools and I would reckon that many of them turned 18 this year. I saw the bios of the BBC boys recently and saw that one of the outstanding players was around 18 and a half years old. His opposite number that day had turned 16 only a couple of months ago. The opposite number was good enough to be there, but I know that having over two years age and experience would have been a massive factor and an advantage.
It will work its way out with next year's year 8 cohort being the first prep year in Queensland, but there is at least another five years to go before this occurs.