I am going to keep my daughter and her boyfriend from sleeping in the same bed.
What makes you not want them to sleep in the same bed?
She is not old enough and she is better off just focusing on her studies.
if it's your house, it is up to you to make that decision because it is a big one. Let your daughter know the boundaries and that they are not to be crossed at any time.
I'm telling her boyfriend this right now!
It is perfectly fine for you to set boundaries for your daughter. Just be careful not to be too strict however because this may simply just turn her into a rebel. Just let her know that it is important to take things like that slowly.