A: They are not going to school today.
B: They don't go to school today.
C: They haven't gone to school today.
D: They didn't go to school today.
Which one is correct if I want to use today
A: They are not going to school today.
B: They don't go to school today.
C: They haven't gone to school today.
D: They didn't go to school today.
Which one is correct if I want to use today
You can use each one, provided that:
A The time is before the school's start
B This feels more like a general statement, used for example for a national holiday
C The day isn't over, and they didn't go to school. (e.g.: if the school is still open in the afternoon, they could still go there)
D The day is over, and they didn't go to school