Has anyone come across this situation?

I've recently been accepted to teach ESL at a new school here in Hanoi Vietnam. However they want me to teach a British curriculum Pearson GCSE English book, which is clearly above their level.

I've tried telling the management that teaching GCSE English to non-native speakers is a terrible idea and that they should be using an ESL English book which has the vocabulary, speaking, listening, writing, reading components but they just seem to not listen and say it's my fault for not wanting to teach their material. I'm trying to explain why it's a bad idea (student frustration, classroom management issues etc. ) but it seems like my advice is falling on deaf ears... thoughts?