I used to teach Intro in Java, followed by AP Computer Science in Java. My scores were okay.
I switched the Intro class to Scheme, but the AP test stayed in Java. My scores went up: a plurality of my students received 5's, and more students got 5's than failed the exam. These are by far the best scores I've ever had and these are the first students who had the HtDP curriculum in the pre-AP course.
The first programming class isn't about language--it's about concepts, good habits, and learning about design. How to Design Programs is a great curriculum.
Todd O'Bryan duPont Manual High School Louisville, Kentucky