working with new classmates is one of my favorite and most hated things to do. For one it humbles me, reminding me that the techniques I take for granted didn't just come to me over night, I had to work hard to gain the skills I have. It forces you to talk out the techniques to the new classmate, giving you a mental picture of how the technique is supposed to work, helping you understand the technqiue even further. And it gives you a little chance to show off in small ways boosting your ego and pushing you even harder. And in self defense pratice you can see how an untrained person, albeit a bit nervous because its the first time training, would react.
The reason I hate working with new classmates is that you can't work on advanced techniques or combinations you have trouble with. You'er stuck doing the four basic blocks and the roundhouse kick. You'er more lible to get injured if sparring or practicng a technique on the new comer.
There are instances where the new comer is from another martial art and those can be fun cause you get to learn about the differences between TKD and the other art from a new perspective. Sometimes here the same retorect, TKD is a sport blah blah blah, but then there are times where the practioner gets all excited cause he can add the kicks he's learned to incorporate into his self defense techniques he's learned.
On the other hand getting nailed in the groin repeatedly when sparring a point sparer(sp?) is really annoying, and not reccomended if you want to have children