My first thought would be that he isnt using the right driver. 85-95 mph clubhead speed isnt the stuff from which 300 yard drives are made. But if he's knocking the 3 wood about 230 he's doing ok. I would hope to see at least 265-270 out of the driver from him. I think i hit my 4 wood about 250 and my 6 wood about 230 (its a seven head with a five shaft i just call it a six) and my driver is about 285 average ranging from 265-300 depending on my creaking bones. I think my clubhead speed is about 105 or thereabouts I know my ball speed off the 3 wood is about 150mph. and I hit the three about the same as the four maybe a few yards more (its a strong 4). So he needs to generate a little more clubhead speed with the driver. Now his three wood goes well enough so maybe check what type of shaft is on it. I would suggest lightening the shaft on the driver to maybe a 60 gram shaft. And maybe lightening the flex (a callaway system 60 firm maybe?) Try him with one of the smaller headed titanium drivers as well, lightening the club further. I assume you dont want to make any changes to the swing since he is solid everywhere else? The only change I would suggest is trying to widen his arc a little with the driver to generate a bit more leverage and trying to get him to pull the hips through a little faster. But those changes can take months to get right, I should know...I did it a few seasons ago.

I wouldn't let him get too fixated on distance as the be all and end all. I know a guy who never moves the ball any further than 240-250 yards who plays quite easily to 4 or 5 and is similarly short with the rest of the clubs, but if your student is ok with the irons he should be able to better that.

Good Luck.