I translated "The student did not come" as "学生没来了" but the answer was "学生没来" (i.e. 了 is omitted). This answer confuses me because it doesn't contain any indication of past action; i.e. I would translate "The student is not coming" to "学生没来".
Why is it that "了" is not required in this case?
Is my answer acceptable? What is the difference?
How would you distinguish "The student did not come" with "The student is not coming" in Chinese?