What about the grade 3 teacher doing NAPLAN? Is it the Prep, Grade 1 and Grade 2 teacher that are more responsible?You're Primary right? I actually think the Grade 3, and particularly the Grade 4 teacher are more responsible for the Grade 5 NAPLAN result than the Grade 5 teacher.
When a year 3 or 5 teacher has roughly 14 weeks with the students to get them ready you cant lay blame on them for results. Yes it might be great to compare each child's progress between the two tests but there are many factors that impact on a child's progress year to year.