[Grammar] past simple or present simple?

[NUCA]

Is it right to use past simple or present simple in this sentence: "She didn't go to school today, because she is ill." or "She doesn't go to school today, because she is ill." I need to know Which is right. Can I use past simple with time expression like "today".

 

[5jj]

Is it right to use past simple or present simple in this sentence: "She didn't go to school today, because she is ill." or "She doesn't go to school today, because she is ill." I need to know Which is right.

Your second sentence is not very natural. You can say:

She didn't go to school today, because she is/was ill. Said at any time after her normal time of departure for school.
She isn't going to school today because she is ill. Said at any time from the time the decision was made up until about midday.

.

Can I use past simple with time expression like "today".

Yes.