How do we know that the Gómez & Gómez DLE Model is effective?

The overall program effectiveness is typically assessed using students' academic achievement on the 3rd, 4th, and most importantly, the 5th grade TAKS in Reading, Writing and Math.  As we continuously stress, the programs with the highest achievements are those that adhere to the  Model the closest, in other words, those with fidelity of implementation.

How do we make sure we are implementing the Model with fidelity?