The aim of this paper is to examine the impact of activity-based mathematics instruction on mathematics performance and investigate those factors, which contribute to the mathematics performance of a sample of children aged between 10 and 12 years. The study was designed to consider the impact of prior knowledge, self-regulation, prior attitude, and reading ability on students' mathematics performance. The data were collected by surveying the students using four instruments: achievement, attitude toward mathematics, self-regulation, and reading ability. The initial results indicated that activity-based mathematics instruction made a significant contribution to students' mathematics performance and mathematics attitude. Students with high prior knowledge and high self-regulation skills demonstrated greater gains in mathematics performance. Students with high prior knowledge also showed a more positive attitude toward mathematics. However, students with low prior knowledge and low reading skills showed the greatest gains in mathematics performance as measured by a retention test. Recent perspectives on the effect of activity-based instruction and the predictors of mathematics performance were described, and recommendations were offered.