Codewars is a website housing thousands of coding challenges for a wide range of abilities. You can search for problems through kyu level, # of users who solved, topics, etc.
Solving problems gives you experience and you can see how you rank against your peers.
You can also see other solutions once you've solved it, thereby seeing alternative ways to code.
For a semi-organized and currated list of challenges, check out Birkel's Code Wars Labs
The George Fox University High School Programming Contest (Formerly the Willamette Programming Contest) is an awesome opportunity for students to test their skills at programming challenging problems. Competitions are held in March/April with teams of 2-3 students working together to solve about 15 problems in about 4 hours.
Check out the Past Challenges and talk to Mr. Birkel if you're interested in doing more.
Additional contests:
Hewlett Packard Enterprise - CodeWars (Held in early March)
Cyberstart is a series of cybersecurity challenges that are meant to test your ability to program, debug, sleuth, command line, and so much more.
The competition is online and completely free. Students who go far enough in the competition get scholarship opportunities as well as free Cyber Security trainings.
Go to CyberStart America for more information and to get signed up.
The OGPC is an amazing opportunity to create a game and show it off at a competition.
In the fall, the theme is announced and students build a game together to have ready to show off in the Spring.
To date, none of my students have actually followed through with a game to take to this competition... Who will be the first?
Cyber Security
PicoCTF - A cybersecurity Capture-The-Flag game hosted by Carnegie Mellon University
AngstromCTF - A cybersecurity Capture-The-Flag game hosted by highschool students.