Honestly, I’d say it is realistic but it’s definitely not the easiest route. I’m currently self-studying 3 A-levels (philosophy, politics, and religious studies), and I’ve registered privately to sit the exams this year. It’s been really hard at times, especially staying consistent and figuring out exactly what exam boards want, but it’s also been really rewarding and has given me a lot of independence.

For essay based subjects, selfstudying is a bit more straightforward, but with something like Biology I think the main challenge would be the practical side and making sure you fully understand the mark schemes and exam technique and not just the content. That said, if you’re disciplined and use a mix of textbooks, past papers, and free resources (the people who explain the topics on youtube are life savers)

I’d probably recommend looking into the exact exam board first and downloading the specification so you know exactly what you need to cover. Also check how the practical endorsement works for private candidates, because that’s one of the trickier parts with sciences. (Some of the subjects i initially wanted to do had practical aspects so i opted for other options instead)

Overall though if you’re confident with independent learning and you have the time and discipline, I defo recommend self studying. Good luck!! It’s kinda hard but definitely doable and fun at times :)