I don't mind teaching however it isn't my favorite thing to do. If every student really cared to be there and really wanted to learn I'm sure I would love teaching but all the gripes over half a mark end up making any teaching assistant a bit jaded. Although I do love the one on one teaching such as when your supervisor puts you in charge of a project student or a summer student in your lab. Sometimes they can be a pain in the ass but for the most part they are there because they enjoy research.
The first student I ever supervised in the lab was a high school student. She had to do a project or something for her International Baccalaureate diploma (aka "smart kids program"). Heck I had to Google Baccalaureate because I didn't even know how to spell it. Anyways, somehow she ended up in our lab and me being the newbie grad student at the time my supervisor thought it would be a good experience for me to teach a high school students the ropes for a semester. Sure why not. Supervise a high school student in the lab, take two grad courses, TA a 200-level lab, and also do my own research in my "spare" time. Sleep is overrated anyways.
Well that was during my first year of grad studies and today I got a call from that student. It was a nice surprise. I hadn't heard from her in a long time. Sure she came by every so often during her undergrad here but I lost touch with her the last year or so. She told me she is now doing a Masters and is thinking of doing an MD/PhD (see, smart kid!). I was so excited. I like to think that I played a small part in her enjoying science and research. After all her first research experience was with me. Oh it gives me warm fuzzies to see students become interested in science and research and excel at it.
Hmm... wait a minute. This girl was in high school when I supervised her in our lab and I was just starting my PhD. She has since finished high school, got her BSc (no doubt with Honors or even Distinction) , and now she has started her Masters degree and I'm STILL doing my PhD! Dear god! My family is right. I have been in school forever.