OCR was always regarded as the private school exam board. In English Lit , the way this showed itself was often through text choice rather than anything else. This, however, did have the knock on effect of a skewing of ability of the entrants from that board and , therefore, the domino effect (to mix metaphors!) of many state schools avoiding OCR because they felt their , on average, weaker entrants were harshly judged by the examiners who were reading many many high calibre scripts (and , also, tended to teach in academically selective schools). The reforms are meant to have lead to a greater parity between boards. AQA does remain the most popular in many subjects and OCR is still often the one chosen in independent schools.
For my part , I have AQA for English Lit (s'alright, bit restrictive in text choice and not keen on arbitrary connections made inP1 ; quite difficult to plan a route through . AQA has open book, which,interestingly, not all the boards have,I believe) , Eduqas for Film GCSE and A Level (a great exam board to work with but did a 'how high would you like us to jump' in the reform phase which led to very complicated exams and lots of tweaks) and OCR also for film A Level. I have dropped the latter like a ton of bricks after one year because they are so uncommunicative and unsupportive! This is a reputation they have always had and it's deserved!
I am sure when I started teaching there were even more boards : AQA is an alliance of at least two old exam boards. And then there's International exams , of course!