Victorian Department of Education and Training data shows Warrnambool state school students missed an average of 19.7 days of school in 2017.

Student attendance in Warrnambool was lowest among year 10 and 11s, who missed an average of more than 25 days that year.

The number of days absent gradually increased by four days since 2013, and is above the state 2017 average of 17.9 days.

Beyond the Bell action group chair Glenys Phillpot said Warrnambool's secondary and primary schools, both public and private, had raised concerns students were missing school without a reasonable explanation.

"If your child is just absent for five days of school each term, they will miss more than a year of school between prep and year 12," Mrs Phillpot said.

She said the action group now planned to host group discussions with students, to determine the reasons behind absences and reinforce the value of attending school as part of a campaign called "every day counts".

"You obviously miss the learning, you miss connection with friends," Mrs Phillpot said. "You also don't build on that team bonding you get and you just feel less connected."

Warrnambool's Emmanuel College principal Peter Morgan said while the school generally had strong attendance, a "small proportion" were regularly absent. Twenty per cent of students did not meet a 90 per cent attendance marker in 2018, national My School data shows.

Mr Morgan said reasons for absenteeism were multiple and complex, and could involve both physical and mental illness, or families taking holidays during school terms.

"If the student's absenteeism is being caused by anxiety or a health condition, it is very much a matter of the school and family working together, and generally there is also a third-party professional involved," he said.

Mr Morgan said parents and guardians had the "first point of responsibility" to ensure attendance but the school would work with families when difficulties arose.

He said he believed attendance was "a social issue" schools were grappling with and supported Beyond the Bell.

"It's absolutely right that every day does count, and I'd have to say that rarely is missed time caught up unless there is a really sustained and thorough effort," Mr Morgan said.

"What in our society has increased our tolerance of students being absent from school is something I think we need to understand."

My Schools data also shows 84 per cent of students met a 90 per cent attendance threshold at Woodford Primary School in semester one of 2018, while 67 per cent of students met the same threshold at St John's Primary School Dennington.

Warrnambool Primary School principal Peter Auchettl said early years set habits for students in later years.

"If the child is brought through early stages of their life to say it's not OK to be away, you will find a high majority of those kids will be at school in their later years," Mr Auchettl said.

"We try to get the message across to students, if students miss school they miss continuity in their education."

A spokeswoman for Victoria's Department of Education and Training said Productivity Commission data showed Victoria's absence rates were among the lowest in Australia.

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