In the beginning of a speech:-
The school holidays are fast approaching and I am sure all of you parents out there are worried about how to occupy your children.
School holidays ...
Which sentence is grammatical?
I agree with holydragon that both sentences are grammatical. However I disagree that it is less advisable to use "the" if the topic has not yet been raised, such as at the beginning of a speech.
This may be a regional thing to some extent, but I'm not so sure. If you're referring to upcoming school holidays you clearly have a specific holiday in mind, hence "the school holidays" seems appropriate. Furthermore, school holidays are widely important for society, such that even people with no friends or relatives in school are generally aware of them. It seems to me that it is reasonable to expect that anyone you talk to should be at least vaguely aware of which specific school holidays you are talking about, hence "the school holidays" would also be appropriate.
I would be more likely to use just "school holidays" if I had no specific holiday in mind, though I may also use "the school holidays" in that case. I'm not really sure how I would decide between them, to be honest.
If you have mentioned school holidays before the sentence or your audience knows which school holidays you are talking about then you can use the at the beginning of the sentence, but for the beginning of a speech, I think not. Otherwise, I suggest using "School holidays ..." because it is more general. Anyways, both sentences (with/without the) are grammatical.