Grading Autograders

The other day codehs made an announcement about their new autograder. Fellow CS Teaching veteran Alfred Thompson had his say up on his blog where he talked about Mark Guzdial's comment on autograders leading to less creative assignments.

I very much agree that autograders, due to their rigidness lend themselves to less creative projects, but thought I'd write up a few of my own thoughts on autograders.

First and foremost, I HATE GRADING. It's one of the worst parts of my job and grading projects is really hard to do well.

You'd think an autograder would be a panacea.

It's not.

In addition to them being very nit-picky – got an extra space in your output? FAIL. Wrong number of significant digits? FAIL. Didn't handle all those "trick" cases? FAIL.

Since autograders typically check your output against a correct solution, it's going to be limited in what it can grade right and wrong and what's more, it's very limited in the feedback it can give.

These are some of the limitations that lead to less creative projects but that's not my beef with the autograders.

Why do we give assignments? To assess students? Yes, but also to inform our instruction. We need to grade the assignments ourselves because those assignments tell us about our students and teach us how best to work with them. What's more, we really don't just want to see that finished product, but rather, we want to see the process as well. Autograders can't help here.

I do use autograders – and our own locally developed Scheming Bat. I use them for small homeworks and class assignments early on. For bigger stuff, I do it myself.

For advanced classes (AP and beyond) we're all about the GitHub. Not only can I grab the projects at any time but I can also see how projects were developed - logs, diffs, graphs. All give me insight into how the students working. Add in class lab time when I get to interact with the kids and I've got a good sense of my student computer scientists.

In our intro courses, where they're not ready for GitHub, we use Dropbox for sharing and collecting assignments. Not quite as good but we can still see a lot.

At the end of the day, if a teacher doesn't look at a student's work directly, a teacher isn't going to know everything there is to know about a student. I can't imagine a top English teacher not reading a student's essays. We're no different.

It's time consuming and generally no fun but it's a big part of real education.


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