I hear this sometimes: “Everyone knows one-and-done PD is bad.” Here are three reasons that I think the thinking behind this line could be improved.
1. If it's true, then a recent study of 10,000 teachers suggests that “everyone” is wrong.
One of the chief findings of a recent study on teacher professional development is that effective PD is pretty idiosyncratic. Basically, even the buzziest kinds of PD — “job-embedded,” “differentiated,” — aren't silver bullets (go figure), and the titularly maligned “one-and-done” types of PD (all-day workshops, keynotes) aren't useless. Different kinds of PD work for different teachers at different times. 
2. If it's true, then my life makes no sense.
It was at a one-and-done, all-day Kelly Gallagher workshop in Grand Rapids when I started thinking, “Huh — that guy is a teacher who also writes and speaks about teaching. Maybe I could try doing that someday.” That was kind of a big thought for me — it eventually led to this moment in which I add the 302,000th word (or so; see Figure 1) to a blog that has made me the teacher I am today.
It was at a one-and-done, one hour keynote during my student teaching that I heard Ron Clark speak. While I only briefly adopted Clark's eccentric The Essential 55 methods during the earliest part of my teaching career, the process of experimenting with Clark's approach, as well as his energy and passion for teaching, were like rocket fuel at the start of my career.
My anecdotal evidence doesn't prove my point, of course — and I've not shared with you the bad one-and-done PD experiences I've sat through as a teacher. But I don't think I'm an outlier — many teachers I know have had their practice improved or their thinking clarified from one-and-done experiences.
3. Make things as simple as they can be — not simpler.
I'm no different than any other teacher — I've had good and bad PD experiences. But the kinds of PD that have helped me in my work have only one thing in common: they've taken many forms. Every ounce of impact I have on my students is the fruit of experiences as simple as reading a book (or as involved as writing one), as in-depth as the Lake Michigan Writing Project's Summer Institute, as far-flung as the Transatlantic Outreach Program's study tour of Germany, as traditional as quality post-eval conversations with an administrator, as painful as watching film of my teaching, as innovative as a lab classroom experience, as meta as leading PD myself, and as natural as the daily conversations I have with my colleagues, my students, my wife, and my friends.
We just need to be careful with dogmatic sayings like “Everyone knows one-and-done PD is bad.” That's all I'm saying. Statements like that oversimplify a complex thing.
- The Mirage, the study's report, is interesting reading. I especially like the recommendation for how we might reconsider the teacher's job (less grading is implied, p. 38). Also, my sharing of this report is not an endorsement of the reporting organization, TNTP.
Thank you to the many educators who encourage and support teacher professional development around the world.