As a former high-school math teacher and big proponent of Lockhart's philosophy, I highly recommend Phillips Exeter's math curriculum (http://www.exeter.edu/aca

As a former high-school math teacher and big proponent of Lockhart's philosophy, I highly recommend Phillips Exeter's math curriculum (http://www.exeter.edu/academics/72_6539.aspx http://www.exeter.edu/academics/72_6539.aspx). It's entirely problem-based; each night the students are assigned a set of about ten problems, and they do the best they can with them. The next day, they meet in groups of twelve with a teacher (more like a facilitator) who leads them in a discussion of how they approached the problems and their solutions. Although the problems themselves are often quite practical, they are designed to illustrate and reveal over time the abstract concepts behind them, and they lead the students towards finding abstractions and generalities as they go. It's free and publicly available; I recommend downloading them and reading through a few problem sets to see what I mean.