Children who miss school for just seven days a year damage their 'life chances', according to the Department for Education.
Despite the fact that children get 13 weeks holiday a year, pupils who miss seven more days – either because of illness or parents taking them on term-time holidays - are damaging their future prospects.
On the day schoolchildren return from what, to many parents, seems like an utterly pointless February half-term break, the Department of Education says pupils who take even more time off see their prospects of gaining five good GCSEs reduced.
And Education Secretary Nicky Morgan said this vindicates the crackdown on parents who take advantage of cheap holiday deals by removing pupils in term time.
Under new rules, headmasters can only grant leave in 'exceptional circumstances' and local authorities can impose fines on parents who flout the rules.
Mrs Morgan said: "The myth that pulling a child out of school for a holiday is harmless to their education has been busted by this research. Today heads across the country have been vindicated – missing school can have a lasting effect on a pupil's life chances."
Department of Education researchers looked at the performance of children over the two-year GCSE course and were surprised by how great a difference short periods of absence appeared to make.
They found that just 31 per cent of children who missed more than 14 days of lessons over two years got the 'gold standard' of good grades in English, Maths, Science, a humanity and a language.
It compared to 44 per cent of pupils who attended school every day. And just 16.4 per cent of children who miss 28 days of school over two years - the equivalent of two weeks' holiday each year in term time each year - get five good GCSEs.
The average child misses three days' schooling a year due to ill health – meaning just an extra week off a year for a family holiday could make the critical difference.
The Department of Education conceded that the research does not take into account other factors - such as whether parents who take children out of school in term time are also less strict when it comes to completing homework.
However, they said it supported anecdotal evidence from teachers that pupils struggle to catch up on missed lessons and can be left permanently trailing if they miss just a small portion of the curriculum.
What do you think? True or more pressure on parents not to go on holiday in term-time?