What is the ruling on a teacher working during the lesson at the time of Dhuhr prayer and missing the congregational prayer?

Congregational prayer is obligatory for resident men. If its time conflicts with class time, then congregational prayer must be prioritized, and then you may return [to class]. However, if that is difficult and leaving work is arduous for you, there is no impediment to continuing to teach. Strive to perform it after the class with another congregation. If that is not possible, then Allah does not burden a soul beyond its capacity.