It's realy good that you help each other with working towards your exams. But, imagine the benefit you would get from having people in the same form as you who have already done the exams that you are going to do. Remember each form will also have sixth formers attached to the group as well who will be a great source of help with things like this.
Mr Astbury is right - you will still have other students from the current Year 10 in your group and the benefit of students from other year groups who have been through the stage of schooling that you are at. You will also benefit from a huge increase in support from your tutor who will only have to track the progress and advise four students in each year group rather than twenty eight students progress and needs. This increases the support that the current Year 9 & 10 will enjoy in their GCSE years and in fact gives them an advantage over students who have only been in the year group pastoral system.
Mr Bodey