To the OP,
I would seriously counsel against trying to plan so far ahead.
You are, I assume, only 16 or 17 if you are yet to choose which Uni you're going to? While some interest in what the MC/US firms do and pay is good, its a little early to be contemplating which degree modules you should be studying to help with your TC at Shearman & Sterling.
Don't choose to study law simply because you like the look of the $ signs. If law is something which interests you then go for it and try to get into the best Uni you can. When choosing a University, its position on a league table should not be your sole criteria.
When you start studying law, keep an open mind about what might be an interesting career and don't just get dragged onto the London vac scheme/TC conveyor belt. There are masses of things to do out there which can be far more satisfying that corporate/commercial law. Trust me, I speak from experience.
One last thought for the day. You've posted lots of threads asking for people's advice. That advice has been freely given. Perhaps a little 'thanks' every now and then wouldn't go amiss?
Chalks.