Third A level for Mathematics course: CS vs Psychology

Do physics - it ties very nicely with maths, especially if mechanics are your thing; universities view the physics a level in a very high regard aswell.

CS 100%, you will code a lot using python, MATLAB and R in a maths degree.
Tech skills are probably the most respected skill once you get to the jobs market so you should get this done early.
Psychology is a humanities subject disguised as STEM and there's very little employment to grad ratio.

Edit: Don't listen to that Rory bloke. For uni admissions grade>subject all the way. If you aren't good at Physics there's no point studying it because if you get a B then you can say goodbye to Cambridge and UCL.

You play your cards to your strengths and don't be forced onto someone else's home field advantage. Remember this and you will get far not just for uni but for life.

99% of Unis are perfectly okay with Psychology - they will always tell you which subjects are essential or are 'preferred' and for the 3rd subject it can usually be literally anything.

Its only the 'up-themselves' place like KCL, LSE and UCL that have daft 'lists' of subjects - this is mostly to exclude the riff-raff rather than an academic necessity. Go somewhere normal instead.

I'll apply to Mathematics courses. So I'll have to do Maths and Further Maths for sure.

Not sure what to choose for the third subject. I am personally interested in Psychology, but some unis don't seem to particularly prefer psychology as a third subject.

For instance, most of the Cambridge colleges say Physics would be a useful subject.

UCL says Biology, Chemistry, Computer Science, Economics, English Language, English Literature, Physics, and Statistics preferred.

I'm bad at physics, so I'm not really considering that. Rather, I've been coding for about 5 years now, so Computer Science can be a science subject that's less intimidating for me.

Would there be a significant difference between choosing CS vs Psychology as a third subject for Mathematics application?

I can only speak for Cambridge, but, since you mentioned them specifically, I assume you're interested. In short, it really doesn't matter. I did neither (my others were Chemistry and French) and I have a friend that did Music as his third and other friends that did a whole bunch of other courses as their thirds or fourths. They care about your ability to do Maths, so having Maths and Further Maths and any acceptable third option (alongside STEP) will suffice. There is a coding project in second and third year where CS may be useful for your ability to do it, but not really for admission, especially as the coding project is "optional". I did Computer Science GCSE and that was pretty sufficient for my coding abilities.

Note that this may be different if you are specifically applying for the Maths with Physics option, where you may need Physics (check as it may vary by college) but I assume you weren't aiming for this.

Thank you so much for all the details from your experience!

Yes, I'm definitely interested in Cambridge, but I'm not too confident that I could do 1, 1 in both STEP exams. I'll still give it a shot!

Maths with Physics option is not something I'm aiming for at all. Furthermore, I'm a bit intimidated by the Cambridge curriculum as I remember one of the tutors there saying mechanics is important. Mechanics is a bit of a trigger word for me as I'm not great at physics. Would you say there are lots of physics aspects in your studies? or is FM Mechanics is enough?

It's quite a bit of a surprise to hear some even did Music! But may I ask if these people had IMO/BMO medals or have experience with UKMT challenges so that the admission committee won't care whether the subject was Music or French? I have created an imaginary cohort of mathmos, where literally everyone is such math competition winner. So I wonder if just getting A* in Maths and FM + 1, 1 at STEP will ever be enough to get in.

In the first year, there is some Physics-y Maths; however, it is all taught through a very Mathematical lens, i.e. you do the calculations but you're not expected to know the Physics behind it. Mechanics in this course could be useful but, honestly, I've never found it to be an issue. I didn't do any Mechanics in Further Maths, and, since I did Maths in Year 12 and Further Maths in Year 13 and then a gap year, it had been more than two years since I had done any Mechanics at all when I started and I never found it to be an issue. After your first year, there are no strictly mandatory courses (though there are some that not taking would limit your options significantly) so if, like me, Mechanics wasn't a strong point, you can avoid courses that need it. Furthermore, there is an optional refresher course in Mechanics offered in first year tailored to those with little to no Mechanics in their educational system (I hear IB doesn't have much Mechanics in its Maths-equivalent options, only Physics, but I may be wrong).

The guy with Music didn't do IMO and I don't think he did BMO though I may be wrong. With the exception of Trinity, which seems to really like Olympiads, most colleges aren't that fussed about them; the style of an Olympiad is really different to that of undergrad so they're not super relevant if I'm honest. I did BMO1 but in Year 13 as a gap year student and my DoS (Director of Studies) said that that wouldn't have made any real difference.

I think a useful way to think of the third A-Level dilemma is that STEP has more Maths than Physics or Computer Science will ever have and that's really all they care about. It's not really about being well-rounded as you will just be studying Maths. You can show your ability through Maths, FM and STEP; doing something 'Maths-adjacent' doesn't mean that you're better in any way at Maths.

Thanks a lot once again. So it's really about 'ability to do Maths' rather than anything else.

How would you define that though? How is it measured at the Cambridge Maths department?

I'm confused what my focus should be. Solving problem sets over and over again to get proficient at it? Or try to 'think deep' as much as possible? The problem with 'think deep' is it often derails me from the problem sets and etc -- So I've been thinking that this period for me is to learn basics. I should try not to overthink and focus on solving problem sets, but then I keep on feeling like there has to be something more for me to be as good as those who get offers to be mathos.

I don't think it's 'measured' per se, but what I meant was that it's not about extra-curriculars or well-roundedness (up to a point).

I find solving problem sets works quite well for me, but I also enjoy doing so, so it may be better to have a look at what works for you.