Euler Circle is a mathematics institute in the San Francisco Bay Area dedicated to teaching college-level mathematics classes to advanced high-school students. Each quarter, one class is offered; past topics include abstract algebra, complex analysis, and algebraic geometry. Classes meet on Tuesday and Wednesday evenings for 10 weeks, with new material being presented on Tuesdays and students working on problems on Wednesdays. In the last week of class, students give presentations on topics of their choice related to the class material.
Euler Circle is run by Simon Rubinstein-Salzedo, who is also known for being the person after whom Simon's Favorite Factoring Trick is named.
You can learn more about Euler Circle by visiting the website here.