Launched in 2016 and led by The Hong Kong Jockey Club Charities Trust (The Trust), CoolThink@JC is scaling the study of computational thinking to primary 4-6 students across the territory. By early 2023, the CoolThink network had enrolled 204 schools in six cohorts, achieving a critical mass of schools that will have adopted the 14-hour curriculum by the end of the scaling period. Moving forward, the CoolThink team is pursuing a two-pronged mission: supporting the continued success of the 200-plus schools within its network and promoting a successful rollout of computational thinking education (CTE) to all remaining Hong Kong primary schools. This second report from SRI International's ongoing study of CoolThink implementation at scale examines the progress made by the CoolThink@JC initiative at midline. Based on a variety of data sources, it describes CoolThink implementation at the classroom and school levels in 47 Cohort 3 schools after two years of CoolThink adoption and in 52 Cohort 4 schools after one year. In addition, the report describes the development of an emerging ecosystem that can support CoolThink@JC at scale in Hong Kong, and factors that the authors expect to be important to a successful adoption by the full breadth of primary schools in the territory. [CoolThink@JC is created and funded by The Hong Kong Jockey Club Charities Trust, and co-created by The Education University of Hong Kong, Massachusetts Institute of Technology, and City University of Hong Kong.]