Main Article Content
Concept mapping instructional strategy is one of the innovations in the teaching and learning of science and biology in particular. Previous studies have reported that teachers and students experienced difficulties in the use of concept mapping. Hence, this study investigated the effects of Concept-mapping instructional strategy on senior secondary school students’ achievement and retention in biology in Lagos, Nigeria. Quasi-experimental research design was adopted for the study. The population comprised all senior secondary school two biology students. Two intact classes of SS II students were involved in the study. The research instruments used were Biology Achievement Test (BAT) and Concept-Mapping Based Lesson Plan (CMBLP). The reliability of the instruments was 0.75 and 0.82 respectively. Three research questions with corresponding three hypotheses guided the study. Analysis of Co-variance (ANCOVA) statistical tool was used tested the hypotheses at 0.05 level of significance. The results of the study showed that: (i) the experimental group performed better than the control group, that is: concept-mapping affects students' achievement and retention; and (ii) there was no gender influence on students’ achievement. Based on results, it recommended among others that teachers should be encouraged to adopt the use of concept-mapping instructional strategy in teaching senior school biology. Also, male students should be encouraged to better their achievement and retention just like their female counterparts.