Learning Math has never brought all exciting experiences for most students in their learning process. Teaching Math therefore has never been as easy as a pie for teachers either
especially for those working in high-school settings and assigned the responsibilities for providing the core knowledge of certain concepts and formulas in a limited time frame and then making students fully understand and be able to demonstrate their application of what they learn to real-life situations. In this regard, this article focuses on the implementation of activity-based Mathematics classrooms following the theories of Project Based Learning, Learning-by-Doing theory, Service Learning, and Inquiry Based Learning to make Math lessons more engaging for the students. Throughout the article, the teaching process is illustrated through school-based examples at Lawrence S. Ting School (Dinh Thien Ly) Junior High School for students in grades 8 and 9. The activities incorporated the theories mentioned earlier with the aim of not only improving student's abilities in solving problems by completing a designed task but also creating meaningful and fun classes. The results show that they have a profound impact on student achievement for more than two years.