Orit Hazzan Judith Gal-Ezer Lenore Blum A model for high school computer science education: the four key elements that make it! 281-285 2008 SIGCSE http://doi.acm.org/10.1145/1352135.1352233 conf/sigcse/2008 db/conf/sigcse/sigcse2008.html#HazzanGB08