The Government's expected to confirm they will be reducing class sizes for students in years 4 to 8 on Monday.
Those year groups have the highest student to teacher ratio, with one teacher to 29 pupils.
NZEI President Mark Potter says that over a generation of teachers have been saying that the teacher-pupil ratio for those students needs to be reduced.
"So it's a very important time for teachers to be able to give the best time they can to children, but it is difficult with so many more children in the class."
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