Artificial intelligence (AI) literacy has become an important component of science, technology and engineering education, but many K-12 implementations still face fragmented content, limited hands-on resources and insufficient alignment across school stages. This case report presents the design and early implementation plan of an adolescent AI science education project in Tianjin, China. The project integrates a stage-based curriculum for upper primary, junior secondary and senior secondary learners with a locally developed AI practice kit, sensor-based embedded experiments, an online course resource system and school outreach mechanisms. The curriculum begins with Scratch and introductory Python for programming thinking, extends to Python data structures and sensor control in junior secondary school, and culminates in embedded AI projects, automatic obstacle-avoidance vehicles, speech recognition, natural language processing and voice dialogue systems in senior secondary school. The case is analyzed against computational thinking, AI literacy and the AI4K12 five-big-ideas framework. The results of the design process suggest that a curriculum-plus-practice architecture can reduce the distance between abstract AI concepts and student experience, while supporting progressive development of logical thinking, problem solving, innovation awareness and responsible technology use. The paper contributes a replicable implementation model for AI science popularization projects that combine curriculum resources, hardware products, teacher support and online-offline dissemination.