Latest figures show almost a million children missed at least one day of school in England to go on holiday last year despite the threat of fines.
The Department for Education said term-time holidays now account for a quarter of unauthorised absences from schools.
Last year a father in the Isle of Wight won a case at the High Court to overturn a £120 fine imposed for taking his daughter to Florida during term time.
Isle of Wight Council appealed against the verdict and Jon Platt's case went to the Supreme Court in January this year, which reserved judgment.
However, teachers said fines were a 'blunt instrument' and the problem was the lower price of holidays in term time.
Russell Hobby, general secretary of school leaders' union NAHT, said: 'The cumulative effect of missed days can be harmful to children's education.
'The best way to ensure children are learning and progressing is for them to attend school during term time.
'However, the system of fines is clearly too blunt an instrument and in many cases it drives a wedge between schools and families. The real problem is holiday pricing.'