I currently coach our school's CyberPatriot team. (You can find information on the CyberPatriot competition here.) We are heading into our second year of competing. Last year we did pretty well for being a more casually organized team, but I'd love to bring in a stronger curriculum.
There are helpful training modules provided for coaches, but for more advanced vulnerabilities, independent study and research is necessary for achieving at the highest level in the competition. In particular, the images students must "secure" encompass a wide range of operating systems. Last year had Windows 7, Windows 8.0, Windows 8.1, Windows 10, Windows Server 2008, and Ubuntu 14.04. Additionally, students used Packet Tracer to learn networking security through the Cisco Networking Academy.
The bottom line is that there is a ton of potential information to cover, and there is a precise way to succeed at CyberPatriot. This page explaining how the competition works details the point system: basically you earn points for doing a precise task in securing the system and lose points for making it less secure.
My question is this: what resources can I use to strengthen my students' ability to succeed in this competition? For context, they are doing it as an extracurricular activity, and any resource that is engaging for students to work though on their own is a bonus. They are highly-motivated, but since there is so much out there, it's hard to know where to begin since cybersecurity is not my background.