Last year, my kids were torturing me about playing the bass. They said that playing bass was pointless, and they couldn't hear it anyway. So I turned off the bass in my Honda for a good long while. It didn't take them long to get to the point where they were begging to have the bass back. Now they can pick out the basslines. It's ugly out there without the bass
Another thing about the bass: if the student has hearing problems, he might well have a very hard time picking out the deep tones of the bass. If he's still having serious problems, you could suggest a hearing test.