Generally for photos of the flightline you'll have to go through Public Affairs, which in turn evaluates your request and either approves or disapproves it. If they approve it, they will generally give you a letter generically signed by the Wing Commander and Security Forces Commander stating you have permission.
For a JROTC trip, you might be safe just being very discreet when taking photos on the flightline, especially since you'll be in a larger group, and taking a tour of the flightline. If Security Forces catches you though, and cares, they will more than likely just ask you to delete your pictures. For further guidance, contact Public Affairs first and they will more than likely be able to assist you.