Uf, medieval is a hard point.

I have few colleagues that are quite proficient when it comes to reading medieval stuff (usually legal documents, Church conclusions and similar), including myself, but understanding anything classical is above us. But sometimes I think that it is also a bit vice-versa. A classicist can have a hard time dealing with texts of this kind, especially when they ought to translate something, since they lack historiographical training.

I think it all depends on what do you want from you language knowledge. Reading =/ speaking =/ understanding.

One could know all the fancy pronunciation stuff and basic phrases and sound "better" while reading out loud than somebody like Mary Beard, or yourself or myself, which are aiming at something completely different. And vice-versa.