At Ashwell State School, west of Ipswich, 100 per cent of Prep to Year 3 classes were over target, although the school only had 52 students last year.

Schools at the top of the list included Gowrie State School, with 57 per cent of classes over target and Deception Bay State School at 53 per cent.

Eagleby, Federal, Flagstone, Giru, Laidley, Machans Beach, Nobby, Oakwood and Wartburg state schools were all at 50 per cent.

Across Brisbane, 6 per cent of classes were over the student target last year, the Gold Coast recorded 5 per cent, Ipswich 4 per cent, Logan 5 per cent, Redland 11 per cent and Sunshine Coast 5 per cent.

However, the score card for class size has been steadily improving in recent years, despite 34,200 more students on the roll call in 2017 compared with four years earlier.

A Department of Education spokesman said the vast majority of classes for 2017 were well within the agreed class size targets.

"Class sizes have improved in recent years as a result of the Queensland government's commitment to 875 extra teachers over those required for enrolment growth," he said.

The spokesman said class size targets were used by principals as a guide in the formation of classes, but they did not represent a maximum.

"For example, a class may be formed one or two students over target to keep students of the same year level together, rather than forming a multi-age class," he said.