The previous two implementations of CPS were done with high fidelity, the HAT studies in a controlled lab environment and the strategy writing implemented by a set of lecture and discussion instructors who agreed to follow a common regimen for an entire semester. In high schools there are numerous constraints that work against high fidelity implementation. Those include varying levels of teacher expertise in physics and teachers' teaching styles, and time pressure to cover content and to administer mandated tests. All of these constraints limit the amount of time that can be spent experimenting with new instructional techni-ques as well as the amount of time available to administer assessments to measure impact. Because of these constraints, a high school environment offers a good testing ground for CPS's robustness as a viable approach since its implementation would likely vary considerably in fidelity. There are also adaptation challenges in terms of structuring CPS in ways that offered students more scaffolding than would be needed with a college audience.