The intended, perceived, implemented, and achieved curriculum of high school biology classes in Israel was studied using a variety of data sources and research methodologies. The intended curriculum was identified by analysis of commonly used laboratory manuals. The perceived curriculum was captured by procuring the views of teachers and students on the importance and practice of educational objectives associated with learning in the laboratory. The implemented curriculum was assessed by structured and non-structured observations as well as by analysis of students' written assignments. The achieved curriculum was assessed by analysis of a large sample of the practical laboratory matriculation examination papers. In light of the findings, which pointed at too little consideration of scientific inquiry in textbooks and in classes and at deficient mastery of inquiry skills as evidenced by students' answers to the matriculation examinations, a learning module aimed at enhancing students' understanding of the processes associated with planning investigations was designed and tried in a number of 12th grade classes. Examples and results, educational implications, and recommendations are discussed. Recommendations include incorporating relevant chemistry chapters in biology studies and having pre- and post-laboratory discussions. (Author/JN)