Current Education Department guidelines state that principals "must" schedule the contentious ''special religious instruction'' (SRI) classes in the school timetable when accredited and approved instructors are available, but Education Department figures suggest the number of Victorian state schools delivering SRI programs declined by almost a third in the past two years.

In 2011, 940 government schools delivered an SRI program, but by 2013 the number plummeted to 666 - a drop of 274. In real terms, 130,100 students received SRI in 2011, with just 92,808 in 2013.

Christian organisation Access Ministries is the leading provider of instruction, delivering 81 per cent of programs through its weekly 30-minute Christian religious education (CRE) classes.

Joe Kelly has been principal of Cranbourne South Primary School for 15 years, and acknowledged that until two years ago he had been "blindly supporting" Access Ministries' presence. That was until he took a closer look at the actual classes and curriculum.