More than 5,000 children were persistently absent from West Sussex’s secondary schools last year, each missing at least 19 days of teaching, figures from the Department for Education show.
The numbers reveal that 13% of state secondary pupils in the area, 5,438 children, missed at least 10% of their allotted teaching time in the 2016/17 academic year.
State secondary schools are required to provide a minimum of 190 days of teaching each year.
On average, secondary school pupils missed out on at least 10 days of education during 2016/17. In total, West Sussex’s secondary schools lost 417,000 days of teaching over the academic year.
School officials authorised 79% of the time that pupils were absent from secondary schools, most commonly for illness or medical appointments. The remainder was unauthorised, and includes periods of truancy and unauthorised family holidays.
The government defines children as persistently absent if they miss 10% of their classes.
In West Sussex’s primary schools, 4,310 children - 8% of all pupils - were regularly absent in 2016/17.
Nationally, the highest levels of persistently absent pupils in England were found in Knowsley, Merseyside, where 23% of state secondary pupils missed 10% of their classes.
Across England, 14% of students in state secondary schools and 8% in primary were persistently absent.
A Department for Education spokesperson said: “Children only get one chance at an education and evidence shows that every extra day of school missed can affect a pupil’s chances of achieving good GCSEs.
“The rules on term-time absences are clear and we have put schools back in control by supporting them - and local authorities - to use their powers to deal with unauthorised absence.”
Local councils can impose fines of £60 on parents who fail to ensure their children’s attendance at school, rising to £120 if not paid within 21 days.
A little over half of absent time across all state schools in the country was attributed to illness last year, 8% to unauthorised family holiday and double that to other unauthorised circumstances, including truancy.
49% of pupils had five or fewer days absence.