The Flipped Classroom model (FCM) is a promising blended educational innovation aiming to improve the teaching and learning practice in various subject domains and educational levels. However, despite this encouraging evidence, research on the explicit benefits of the FCM on K-12 Mathematics education is still scarce and, in some cases, even inconclusive. Thus, the contribution of this paper is to present an action research for investigating the impact of FCM in K-12 Math (Algebra) teaching and learning in order to support and extend the narrow existing pool of works. The action research was based on a quasi-experimental design (using an experimental-control group protocol), with a sample of 40 students, for a full semester of the school year. The results provide evidence for potential advantages in students' cognitive learning outcomes (on knowledge of subject domain), students' level of motivation, as well as better use of teaching time during the face-to-face school-based sessions. [For full proceedings, see ED571332.]