Functional Family Therapy is an evidence based response to conduct disorder in adolescents. When Robert Barnoski of the Washington State Institute for Public Policy studied the programme he found that, on average, fidelity to the model matters. But there were exceptions. Some practitioners who did it their own way got good scores. Others who did it by the book got bad scores. Tom Sexton is one of the developers of the Functional Family Therapy model. Donald Forrester has been a pioneer in bringing good quality research to bear on social work. They discuss Robert Barnoki’s findings, and their implications for public policy.
See here the FFT fidelity findings: