To clarify the matter:

Our gep batch was apparently practically the last one to have the same final-year exam papers across the gep schools. Remember the teachers mentioned something abt dunman setting their own paper one year? That's because the teachers there had trouble using the same standards as the other schools to test their kids... they couldn't complete the syllabus or something on time. At the focus grp discussion, the gep teachers (from rgps, ri, ...) said that now, with so many schools having the gep programme, they never co-ordinate mass things, e.g get-togethers like those maths trails, MEGA, chinese camp, etc. There's now also a policy that each gep school sets its own papers unless the teachers decide to combine with other schools. Results in different standards but it's very difficult to co-ordinate the examinations for 400+ students per batch (anyway the gep teaching in each school is starting to develop distinct sub-cultures).

(One example was a final year exam, same paper given to RI/RGS/ACS/Dunman. There was a predictable normal distribution of distinctions/passes/failures in the 1st three schools, but most of the dunman kids taking it flunked or did pretty badly. Since it was pointless letting kids sit for an exam which most of them would fail, the teachers decided to set their own paper aimed at the student's ability level)

I suspect dunman also sets some of its own papers.