This paper describes the PD program that was delivered during the first year of the study. The main goal of the intervention was to increase teachers' capability to teach positive rational number topics effectively. The program included a 3-day summer institute (18 hours per teacher), five 1-day seminars held during the school year (30 hours per teacher), and 10 days of intensive in-school coaching (20 hours per teacher), providing a total intended dosage that is significantly higher than the dosage of content-focused PD most mathematics teachers typically receive in a single year (Birman et. al, 2007). [For the accompanying papers, see Paper #1 (ED512819) and Paper #3 (ED512821).]