To browse films by subject, you need to click on FILMS on the left side menu. Then, you should scroll down the page until you reach EXPLORE BY and click on the GENERAL SUBJECTS.
If you have access to CAMPUS, you will be able to search by age group as well. To do so, click on FILMS on the left side menu. Scroll down the page until you reach EXPLORE BY and click on the SCHOOL SUBJECTS, then on a sub-subject. You will then be able to access a variety of films on that specific subject. At the top of the page, you will see age groups on a sliding bar. You will be able to slide the cursors on both sides to select the age group appropriate for your class.