Within the science education community, it is widely accepted that quality science instruction is focused on knowledge construction and inquiry. The Ghanaian education system has many hallmark issues that inhibit such instruction, however, including a pervasive teacher-centred pedagogy, lack of laboratory materials, and minimal support systems for teachers. The Practical Education Network (PEN) is an organisation that has been working to address these problems by training science teachers to utilise locally available, affordable materials to teach topics in the national science curriculum in a hands-on manner. To study the impact that the use of the PEN approach to hands-on learning has on students' critical thinking skills, attitudes towards school science and standardised test scores, over 300 students in six Junior High Schools in the Greater Accra Region of Ghana participated in a year-long, quasi-experimental study. The data from comparison and experimental groups consisted of scores on a national standardised test, a pre/post-test simulating the national examination, and a pre/post student survey. The data were analysed for any differences between the two student groups over time. The findings indicated that the PEN approach had a beneficial impact on students' attitudes towards school science and standardised test scores. There was inconclusive evidence of the impact of the PEN approach on critical thinking skills. The findings suggest that the PEN approach may positively impact science instruction.