Every senior at Woodside Priory has to complete a senior project, a demonstration of skill or expression or service to the school that in some way puts a bow on your high school experience. There was a range of impressiveness - some students learned new skills, or put on a theatrical performance, or performed athletic feats, while others did minimally-researched presentations or rudimentary art pieces.
At the time I was very interested in psychology and felt motivated to make something intersting, though, and so I reached out to an expert on school counselling for advice on how to start a program at my own school. Hilary Roberts was more than willing to help, and within a couple weeks of my cold outreach she agreed to be my mentor for the project! Under her guidance I designed a training schedule, recruited a cohort of students who were interested in the project, and taught them how to effectively speak to other students about their issues.
From this experience I learned how to be a leader and a teacher, and I became much better at understanding nuanced interactions with people. As with being a TA, in order to teach a subject you have to know it inside and out, and so having to teach emotional intelligence and effective communication gave me a lot of practice.