The purpose of the study was to design and develop performance based task to assess laboratory reasoning skills of senior high school biology students. The research design used was survey. The target population was all biology students in the nine schools that offer biology as elective subject within Sekondi-Takoradi Metropolis. These schools were of three types namely single sex males, single sex females and mixed. The Cronbach alpha values were: 0.70 for Task I and for Task II, 0.83. Mean, standard deviations, frequencies, percentages were calculated while independent sample t-tests were performed. The skill of reasoning did not markedly vary between male and female biology students in the sex schools. It is recommended that Biology teachers who handle both sexes must be encouraged to use performance assessment as a means to improve the reasoning skills of students.
Keywords: Assessing; Reasoning skills; Academic achievement; Types of schools; Performance.