I got extra time for my AS Level exams last summer. I'm not mentally disabled, but I had received a cancer diagnosis only a couple of weeks before exams were about to start and had to start treatment immediately. The majority of my exams were just one or two days after I had a chemotherapy cycle and trust me when I say the chemo knocks you for six. Not only were my thought processes slower because the chemotherapy was making me way more tired them usual, but a recent cancer diagnosis can really make it hard to focus. I was given extra time, rest breaks, and 20% special consideration... I was also unable to take two exams because of complications with treatment and for those the exam board had to look at my coursework and the grades the exams I did take and give me a predicted grade for that paper.
People can say what they want about whether they think it was fair I got these concessions or not. The exam boards approved the applications made by my college, so if they thought I was entitled to it, then I was entitled to it.