can u sit an exam privately when studying the subject at college

so if u want to sit your a level exam privately while you are doing that subject in year 12 in college, can the college disallow you to do so?

I just need to double-check the scenario. You're currently enrolled in college, in Year 12, and are being taught a particular A level subject. You have no intention of sitting the actual exam with this college and instead intend to pay a different exam centre to sit it with them. Have I got that right? What would be the point?
You wouldn't be able to register to take the same exams with both your college and the external exam centre at the same time. Your college will likely register you in the January or February of Year 13. So you'll need to tell them at that point not to register you for the exams. I don't know quite what their reaction would be. Probably confusion, as it's difficult to see what you plan to achieve by doing this.

So I'm in year 12 and I intend to fast track my a levels by doing them all this year. I don’t do 2 of my a levels that I want to fast track, in college. I only do one of them. I am going to do those two a levels privately this year. In college I do two a levels and a core maths as level, which means that next year I will have to repeat the core maths even if I pass because the college gets funding only if a student does 3 a levels, now, I don’t want that and for the two other a levels that I’m studying, I’m only interested in one of them and had to choose the other because there wasn’t space in my desire course. I don’t want to do another year, if I can pay and do them all in this year as I will be able to do the three a levels I want and not repeat an exam that I have already done.

Thank you so much for this, but if I'm doing the first year in subject A in college and intend on doing it privately too this year, will I be able to register myself for the exam privately? I don't know if colleges register you in the first year and if they already have/even if they have, if I choose to register myself privately, can this affect my grades or ucas application? I mean the exam I will register for privately is for the 2025 entry and even if my college has registered me it would be for 2026 entry, but I don't know if universities know or take into account all the exams you are registered for?

Your college won't enter you for the exams until the beginning on Year 13 (likely in January or February) specifically because some students will opt to drop a subject at the end of Year 12.
Doing this won't affect your grades.
In terms of your UCAS application, which I assume you'll be completing shortly, how were you planning to get an academic reference or predicted grades (both for your college-based and private exams)?