According to Blackman, putting in the extra hours is actually quite enjoyable.

"I've always found it fun to hang out in the terminal room at 3 in the morning with the...students finishing, or starting, their assignments," he said.

Not Easy to be Hard

While most students in the sciences accept undergraduate TFs as a fact of life, their presence does raise some interesting ethical issues. Perhaps the stickiest of these is that of fairness.

To maintain fairness in his course, Leitner says that assignments are graded according to very detailed and precise grading standards, and sections are assigned so that no TF knows any students in his section.

In smaller, upper-level computer science courses, however, this is often simply not possible.

Blackman, a teaching fellow for CS161: "Operating Systems," says that because he already knew almost everyone taking the class, there was no way he could avoid teaching and grading his friends.

"The nice thing about CS is that you can be reasonably certain that you're grading objectively and fairly," he said. "No one's ever appealed to me as a friend for a personal favor when I've been a TF."

But Piotr Dollar `02, a Mind, Brain, Behavior concentrator, says that when it comes to handing in assignments late or getting extra help on problem sets, undergraduate TFs can be more accommodating than graduate TFs.

"It's easier to get away with things sometimes because you're already friends with them," he says.

Kevin C. Gold `01, a teaching fellow for CS50 last semester, says he thought grading was the most difficult aspect of TFing his fellow undergrads because it occasionally required him to decide whether or not to pass students who are really struggling.

"It's tough to be mean once in a while and not accept late assignments, or stick with an original grade, because a lot of it is entirely up to the TFs," he says. "We like being liked, but we also have to be just."

Despite the trials of grading, though, Gold says the experience has been very rewarding. He says TFing this year has not only given him the opportunity to try out teaching, but it has helped him decide whether or not he wants to go into academia.

"As a job, of course, it's wonderful. It feels as if I'm getting paid for doing a strange combination of academics and community service," he says.

"I'd definitely recommend doing it to anyone," he adds.

-Staff writer Camberley M. Crick can be reached at crick@fas.harvard.edu.