Ask HN: How should one teach high schoolers to code?

Hello, Hacker News. I'm a high school student in Portland, Oregon and I have volunteered to setup a programming course in my high school to help bring course diversity to the public school system and bring better opportunities to young people.

Treehouse (http://teamtreehouse.com) is sponsoring the class of 15 or so students and each student will have a Treehouse membership for free they can use to study at home. I've been programming both front-end and backend web development for about 5 years now, but have no teaching experience.

My question to you is, how should I tackle teaching programming & app design (HTML, CSS, JavaScript, Ruby, Objective-C) to students who know nothing about it in a short 4 months?