There is a yearly Master The Mainframe competition for students (but anyone can participate, get an account and do the exercises and go through the materials). It's fun. z/OS is completely alien for someone who grew up in a Windows/Unix ecosystem.
Also IBM is launching a new program for students called "IBM Z ambassadors" trying to reach students and evangelize about mainframes... I know it because Im currently an IBM Z ambassador.
https://zambassador.com/