IELTS was invented by UNIVERSITY OF CAMBRIDGE, BRITISH COUNCIL and IDP altogether. IDP and British Council conduct IELTS Test but they do not prepare them. All tests are compiled by English Language Assessment which is one of the joint owners of IELTS.
As to scoring, your Answer Sheet is being checked by trained examiners who have clear instructions that what answers should be considered correct and incorrect. All the modules LISTENING, READING, WRITING and SPEAKING are marked by trained examiners.
All modules band scores depend on how you attempt the test and how you write your answers. On the basis of your correct answers you get the bands and after that calculating
all the modules score cumulatively overall band is given to you.
Both BC and IDP test level is the same because they both don’t write the test. All the test content used at the BC and IDP are assembled by Cambridge English Assessment which is one of the joint owners of IELTS.
IELTS EXAMINER AND MARKING SCHEME AT BC AND IDP:
Both the BC and IDP examiners are trained in the same manner and with the same guidelines.
Both the BC and IDP mark on the bases of right and wrong answers in listening and reading and scores are calculated on the bases of the right answer.There are no difference in marking.The same criteria goes for speaking as well as for writing too.
This is really a very tough thing to decide trhat where shall a candidate pay for their exam. As per the feedback taken from many students and results analysede, we will recommend to go for IDP as your first choice and if in the very first attempt you unable to achieve your desired bands than you may switch to British Council.