CS High School teachers in Texas must pass the CS 141 certification exam in order to teach CS Courses. The WeTeach_CS Certification Prep program developed at the Center for STEM Education at the University of Texas at Austin was developed to provide review and practice for teachers interested in preparing for the 141 Certification Exam. The program started as a face to face workshop bringing 20–40 teachers together for 2 days of review of key CS concepts and understandings. Over 150 teachers have participated in that course since it was first offered in the summer of 2015. Since then a 6 week online EdX Edge version of the course was developed and offered for the first time from June-August of 2016. Over 1000 teachers signed up, and about 500 actually participated by watching and reading prepared materials, doing practice exercises and taking quizzes.