You notice someone in your class is being sexually harassed by a fellow student or teacher.

If you have their cell number or their social media account you can fire them a private message just letting them know that you are seeing what is going on and ask them if you can help in any way. Alternatively you can pull them aside after class, if you need an excuse just say that you need to ask them a question about an assignment, and let them know that you have noticed what is happening and you are available if they need support or if they need a witness' statement.