Since the title explains itself, I can dive right into the reasons.  There’s not always a need for a long, drawn-out introduction!

1. I’m a meteorologist, and we don’t do that.

Put very simply, we don’t get a chance to “make up” for a bad forecast.  We can only learn from our mistakes, move on, and do better the next time.  It’s illogical to think that a forecaster’s mistakes — no matter if they are major or minor — can somehow be washed off his record by doing bonus work.

An example of minor mistakes: the forecaster who continually has a warm bias to his temperatures.  Once you realize what you’ve done wrong, fix it!  Explaining to people why you made the mistake is important, yes — but does not absolve the mistake.  (See #2 below for more on this.)

A major mistake: missed forecasts can have fatal results.  In a recent 5-year period, 17 tornado fatalities occurred without a tornado warning being issued (Brotzge and Erickson 2009).  There is no apology great enough to overcome this one.  I know this all sounds painfully harsh and trite to those who aren’t as familiar with the forecast process.  But put simply, in our field these are the lessons we face every day.  I’m a firm believer that students should experience science as science is practiced, and a no-extra-credit policy is a clear application of that principle.

2. My ideas of sound pedagogy don’t support that model.

Four reasons instructors may offer extra credit are given in this Faculty Focus blog post from 2011.  None of them convince me.

• “It reduces student anxiety and builds confidence.”

This is the only one that holds some water to me.  But this is exactly what practice assignments and homeworks should be designed to do, right?  Build confidence so that students can perform well on major assessments?  Aren’t we already supposed to be designing our courses to that students are well-prepared for exams?  I don’t understand how something like attending an evening seminar about a peripheral topic (a classic extra credit idea) builds confidence.

• “If learning is the goal and students haven’t learned important content, extra credit offers a second chance to master the material.”
• “Not all students ‘get it’ the first time.”

Teachers of college writing know that revision is a key to students improving their writing skills.  In the hard sciences we might use the word practice, especially in meteorology where forecast opportunities are fleeting and revisions to previous work aren’t possible.  I don’t remember but I’m pretty sure my first few forecasts as an undergraduate were awful, and that they improved with repeated practice (to the somewhat less-awful state they’re in now!).  Our assignments and courses should be arranged to give students multiple opportunities to master difficult content before a major assessment takes place.  When we don’t provide this structure, we are less effective teachers.

• “Students are motivated to do it, so why not capitalize on this motivation by creating a robust learning opportunity.”

It’s a bit cynical but to me the implication here is that students aren’t motivated for ordinary classwork.  I certainly hope that’s not the case!  Every learning opportunity should be robust and motivational.  If it’s not, it doesn’t belong in our classroom.  Why should we relegate our most creative assignments for extra credit opportunities that may get done by only a handful of students?

One thing to point out is that I differentiate between large, formal “extra credit” assignments and the rare “bonus” questions that occur on a quiz or an exam: Michael Leddy offers a nice example and his take here.  Most often, I use those to help me scale exam or course grades to better align with student expectations (I’ll rant about the insistence of a 90-80-70 letter-grade cutoff some other time).  But my students can attest that I do this about once per course and is part of an assessment that already exists.  My bonus questions are always opt-out (right there on the page for you to try), not opt-in (available only if you ask or by doing something else external to class).  I’ll avoid saying much about the ethical issues of opt-in extra credit, too, beyond saying that they terrify me.  Is the extra work only available to students who ask?  Are they allowed to tell their peers?  What if someone can’t attend that special guest speaker’s talk because of their job or family?

So there you have it.  Let’s make our coursework compelling the first time ’round, and let’s create assignments that are not busy work but help students learn what we truly want them to do.  That way, they get it right when the grades are on the line.