Successful teaching and learning of chemistry depends partly on correct use of a teaching method whose activities target most learning senses. Though chemistry enhances students' learning of biology, physics and agriculture on which Kenyan industries and prosperity depend, most secondary school students in Kenya perform poorly on the subject. This study sought to examine how the co-operative class experiment (CCE) teaching methods affect students' achievement. Using a non-equivalent control group design with 521 randomly selected students, the study found that CCE method facilitated students' chemistry learning more than regular methods. Gender did not affect achievement. Neither did school type significantly affect girls' achievement when CCE method was used but it significantly affected boys' achievement with boys in boys' schools attaining higher scores. Since CCE method benefited students irrespective of school type, education authorities should encourage chemistry teachers to use it and teacher educators to make it part of the teacher-training curriculum. (Contains 20 tables and 2 figures.)