The ruling has come about because a dad was fined for taking his daughter out of school for a family holiday to Disney World in the United States, without her head teacher giving permission.
The man from the Isle of Wight appealed against the fine, and at first won the case, but now the UK Supreme Court has ordered him to pay the fine of Â£120.
It means that parents will now have to seek permission from the school and head-teacher to take children on holiday during a school term.
The case has caused lots of arguments because some people feel the price of holidays outside of school terms is too expensive, and many parents feel they should have the choice to go on cheaper breaks during a school term.
The Department for Education said: "We are pleased the Supreme Court agreed with our position - that no child should be taken out of school without good reason."
We've been speaking to some of you, to see what you think about the decision...
The most important court in the UK, has made a decision that means parents are not allowed to take children on holiday during term-time, unless the school agrees.