You could also probably find people to do a remote session via Hangouts or something. Pick some ideas for things you want to cover, or find someone who is doing awesome research that you want to learn more about, and ask if they'll talk to your high school group. A lot of people in info sec like to share knowledge, so I don't think you'll have too hard a time finding professionals to talk with. You might also look around at local universities to see what their Computer Science or info sec departments have going on to get involved with. Also sctf does student capture the flags every quarter (or so) and could be a great opportunity for you guys to get hands on experience breaking things.
As someone who was passionate about helping my local high school once upon a time, let me provide a few resources:
HackerRank: This provides programming challenges, often more in the traditional programming competition style. Programming is an important skill to have, and you could have small competitions with each other there.
Overthewire: Overthewire.org provides various wargames machines that you can play on. Exploit different holes to progress to the next level.
Cybrary: cybrary.it offers video resources for many certifications to help you study. This could be particularly helpful if your school doesn't have any local computer experts or any classes.
Old defcon talks are also awesome resources. There are years of defcon talks and Chaos Communication Congress talks and blackhat talks that are just ripe for watching on youtube.
Good luck finding people to help out.