Will I need to take Physics in grade 11?

Well, I think the only class you definitely need is Biology. However, I strongly suggest taking multiple science courses, as nursing is a science. If your school offers an anatomy class, that would be very helpful. I'm sure by 11th grade you have an idea of the college you wish to attend. You can look up the nursing program they offer and see what science classes you take withing that program. If you would take chemistry, physics, and biology, then you should take them all in high school. I would listen to your guidance counselor before listening to your principal. They are trained to tell you what classes to take and have talked to many students about this kind of thing.