what do you mean by drift?
If your heading is changing, this could be due to the power reduction which needs to be balanced with rudder.
If you the aircraft is moving sideways away from the centre of the runway, there is likely to be a cross wind, which your instructor should teach you how to deal with (I understand there are a couple of ways this is taught so I don't want to confuse you here). It may be he hasn't taught you this yet, and so is trying to get you to land as if there wasn't a cross wind and not worry about hitting the centre line. I wont comment on whether this is a good idea or not...
