Can I hide some of the columns shown in the Find Classes page (list of available classes)?

The order of columns going across the page is hard coded and cannot be changed.  You can hide the With column by deselecting the Show Instructor Nickname setting in your Parent Portal settings.  The Class Enrollment Openings badge in the Class column, and the class Start date in the Session/Start column can also be hidden.  Go to Tools > Parent Portal > Settings and scroll down to the 'Class Enrollment Settings' area and make your selections there.  The other columns can not be hidden or removed.