Don't listen to Jeff. He's obviously retarded himself. No, you don't NEED all A's but the better grades you get, the easier it will be to get into a good Law School. It's really your A levels that will have the most impact. So get the best grades you can at GCSE (aim for C's and above), then work really hard at your A levels and try and get grades above C with them as well. That way you'll be able to apply for a good University with a good Law School.
Studying Law at degree level is a lot different to studying law at any other level. So just get used to study and reading. Good luck