Shopgirl I would say about B2 for an A grade at A level. However some students will go beyond this and the B2 only takes into account the mechanics of language learning not the additional cultural knowledge that is part of the A level course.
I feel I am fluent in one of the foreign languages I speak. By that I mean I can participate in pretty much any transaction in that language. Understand pretty much anything, read novels at a similar speed to my English reading speed, however my spoken language will have a “foreign” accent and I have no doubt that I make some daft grammatical mistakes at times - both are things I think are inevitable if you are not a native speaker but do not, to my mind, preclude you from being fluent.