Yeah I agree with JenKneeFur - it all depends on your uni. There will be a jump from first year, and it’s important not to aim for the magical 40% - really you need to be in the 60% plus range.
However third year is where the dissertation is, and it’s usually weighted more heavily thatn other modules. If you don’t get a TC pre-3rd year then firms will be interested in your dissertation topic, and you will need it to be a strong mark to maintain what are hopefully good grades from scond year.
As with all uni modules, they are tough and in law you need to do well in them all to stand a chance of getting a TC!