The main aim of this study was to investigate the effects of the Remap RT (Reading -- Concept Mapping -- Reciprocal Teaching) learning model on low-ability students' achievement in biology. This quasi-experimental research made use of a pre-test-post-test non-equivalent control group design. The population of this research was 125 tenth-grade students from the Natural Science classes aged around 16 years old. Four classes were randomly selected as the samples, and they were divided into two groups: two classes belonged to the high ability classes, and the other two were categorised into the low ability groups. The students' achievement was measured using an essay test. The results of the test were analysed using ANCOVA. The findings indicated that: (1) students who learned using Remap RT had better academic achievement in biology than students who learned using a conventional method; (2) students with high academic ability had better academic achievement than students with low academic achievement; and (3) low-ability students who learned using Remap RT and high-ability students who learned using a conventional method had equal academic achievement. The results of the research suggest that Remap RT was effective in improving low-ability students' achievement in biology.