The purpose of the study was to design and develop performance-based tasks to assess laboratory observing skills of biology students in senior high schools. The target population was all students in the nine schools within Sekondi-Takoradi Metropolis reading biology as an elective subject. The accessible population was 753 SHS 2 biology students in six schools. 261 students were randomly selected from each of the six schools. These schools were of three different types, single-sex males, single-sex females, and mixed. Mean, standard deviations, frequencies, and percentages were calculated while independent sample t-tests were performed. No significant difference was noticed in levels of proficiency shown for males and females in the various schools surveyed. It is recommended that students from all types of schools and both sexes must be given an opportunity to engage in more activities at the SHS level to sharpen their observing skills.