‘The school will remain closed on 18th Aug.’
Is this correct a sentence ? If it is correct ,then what is the rule of ‘Grammar’ followed

Yes, it is correct.

I don’t know how to answer your second question. I guess any sentence makes use of a number of “rules of grammar”, and I don’t know specifically what you are referring to here.

I thought the grammar rule might have to do with using a past tense verb to describe a future event, but I did not know any specific rule that would apply here.

Well, “closed” is an adjective in this case…

Oh, you are correct! Nevermind :slight_smile:

I knew there was a reason why I did not answer this question previously.