A consortium of school districts from four different states offers online high school science courses. Each online course has a different teacher, who interacts with his or her students exclusively online. Each teacher is an employee of a particular host district in the consortium, where he or she also teaches face-to-face courses. Because students from any district in the consortium can enroll in the online courses, each course may be composed of students from many districts in the consortium. Students work on the online courses at specifically scheduled times in their respective schools' computer labs.

One of the virtual courses is high-school biology. One district in each of the four states is offering a different version of this online biology course. The four versions of the course vary in (1) their user interfaces, (2) the ways teachers interact with their classes, and (3) the availability of the teachers for providing one-on-one help to individual students in the classes. The four versions also vary because each teacher is accountable for teaching to the standards mandated by the state in which his or her host district resides. Each state has its own set of standards. Yet the sets are closely aligned in terms of the concepts and processes all high school biology students are expected to master. A panel of science curriculum experts who conducted an alignment study for the consortium has determined this alignment.

The consortium has hired an evaluator to compare the four versions of the course. The evaluation questions are as follows.

• What instructional approaches are being employed in the four versions?
• what challenges arise during implementation?
• What is the differential impact of the four courses on learning and student engagement?