Science undergraduate courses typically cater to a mixed-learner cohort, with a diversity of motivations and skills. This diversity introduces pressure for designers of the practical laboratory curriculum. Students who are struggling with the course need a series of tasks that begin simply, and transition to more conceptually difficult material. More capable students need opportunities for conceptual extension and creative activity. In this report, we examine an approach we have used to address this problem in the context of a large introductory biochemistry undergraduate class. Rather than attempting to compromise on a single practical series for our 470 students, we devised two parallel but equivalent practical streams and offered students their choice of laboratory experience. One stream (called Laboratory Experience for Acquiring Practical Skills) was designed to allow acquisition of a range of common biochemistry and molecular biology laboratory skills. The other (called Active Learning Laboratory Undergraduate Research Experience) was designed to offer an authentic (but scaffolded) undergraduate research project. We discuss the ramifications and implications of our approach in terms of funding, staffing, and assessment while also examining student motivation, satisfaction, and skills acquisition. We present data supporting the practical and pedagogical value of laboratory exercise streaming to meet the diverse needs of students. We suggest a framework that can be used to pre-emptively identify and address problems associated with a bifurcated practical series and increase the sustainability of the approach. (Contains 6 tables and 4 figures.)