Vogue, claiming that they conspire to make the girls fail is ludicrous; maybe you have a different definition of success and failure.
Saying they control them even after graduation is patently false, and would anyhow not be a technique, rather, a result.
My experience with BY (obviously, not as a student) is nothing like you describe.
The bottom line is that for the most part, the girls come out looking much more like a product of their homes than of their schools.