When The isn't used before the word School ?
If only we are talking About a student or a teacher too.
If you are talking about "school" in general - I am going to school now - you do not need an article.
If you are talking about a specific school [the one on the corner of the street; the one in the park] - I am at the school for today - you need an article.
Teachers work in schools
The teachers work in schools
That teacher works in the school which is on the main street
Students attend school
The students went to school
This pupil has not been to the school to enrol.