A father who refused to pay a fine for taking his daughter on holiday during term time has said parents could face criminal consequences for unauthorised absence if a Supreme Court ruling goes against him.
Jon Platt won a landmark High Court ruling that blocked a £120 fine he was issued when he took his daughter to Disney World in Florida in April 2015.
Two senior judges ruled that he was not acting unlawfully because his daughter had a good attendance record during the rest of the year.
Isle of Wight Council, the education authority that took Mr Platt to court, has challenged that ruling and is asking five Supreme Court justices to overturn it on Tuesday.
Speaking to Sky News ahead of the ruling, Mr Platt said any unauthorised absences - including from illness where a doctors' note was not obtained - could trigger criminal liability for the parents of the 8.5 million children in England and Wales if the judgment goes against him.
He said: "Somebody, somewhere, within the Department of Education should have realised that this was a ridiculous argument to put before the court.
"Of course, they won't say that if they win today, but if they win today millions of parents will be faced with the situation where they could choose to keep their child in a state school and face possible criminal consequences for a single day's absence at school.
"Or take them out and home educate them or move them into the private schooling system where these regulations don't apply, that's not what anybody wants to see but that's what's going to happen if they win."
Mr Platt said the education authority was arguing over the meaning of the term "regular attendance" at school.
Regular is defined as something done or happening frequently.
His daughter had more than 90% attendance during the school year - the threshold contained in the Isle of Wight policy on regular attendance.
The issue erupted in 2013, when new official guidelines for English schools said head teachers could only allow pupils to miss classes in "exceptional circumstances".
Parents have been told by the Department for Education that even a few days out of the classroom can damage children's GCSE results.
A DfE spokesperson said: "Our position remains that children should not be taken out of school without good reason.
"That is why we have tightened the rules and are supporting schools and local authorities to use their powers to tackle unauthorised absence."
Mr Platt had requested permission to take his daughter out of school, but it was refused by the headteacher.
He was then issued with a fixed penalty notice of £60, and then a further invoice for £120, both of which he refused to pay.
But when he was prosecuted, magistrates refused to convict him and the High Court dismissed the council's challenge of that ruling after justices said magistrates had been entitled to take into account the "wider picture" of the girl's attendance record.
The decision caused a surge in term-time bookings all over England, following the 2013 Government-ordered crackdown.
Some 35 English councils have changed their policy on fining after the High Court ruling, according to a BBC investigation.
Another five are reviewing their policy, while 28 have withdrawn fines imposed on parents.