I am doing some research on George Boleyn Dean of Lichfield, a relative of Anne's, and came across his degrees and dates at which he obtained them.  I know nothing of the school system, past or present, in England so am asking for any insight into the following.  Most especially about at which these degrees are normally done, or at which age one first enters a school of this nature in general.

1544 enters Trinity Hall, Cambridge

1552 graduated B.A.

1560 commenced mater of arts

1567 graduated B.D.

1576 taken the degree of D.D., became Dean of Lichfield