Whenever I hear educators promote the idea of “project-based learning” I get shivers from the memory of all the “projects” my kids did when they were going through school. Some were small wastes of time; others were colossal wastes of time.

I keep one such project in my office as a reminder of how foolish some assignments can be. It is a paper mole dressed as Democritus, an early Greek philosopher who formulated a theory that matter was made up of atoms. This project was assigned to my younger daughter as a high school sophomore in — and I can barely type these words with a straight face — Honors Chemistry.

If this had been just a small accompaniment to a paper about Democritus and how his atomic theory presaged the work of scientists centuries later, I might have grumbled about it, but not too much. But the main point of the assignment was to create a stuffed animal. One of my daughter’s fellow students, who made a mole in the guise of Marie Curie, was given an entire letter grade lower because the mole didn’t look sufficiently female. This was serious business because the project counted for 25 percent of the semester’s grade. The student’s inability to have his mole wear a beret with sufficient élan, in other words, went on his permanent academic record.

Why a mole, you ask? It’s a chemistry pun — a mole is a basic unit of measurement in chemistry, and chemists around the country celebrate National Mole Day in an attempt to interest kids in chemistry. I’m sure there are ways to make the mole pun work for both student engagement and student learning. My daughter’s class project, however, mostly served to teach kids about sewing and pasting.

So that explains my prejudice against school projects.

But that doesn’t mean I don’t see how powerful projects can be in driving student interest and learning. When my colleague Marni Bromberg and I visited Atlanta’s Drew Charter School, which I write about in this week’s Huffington Post column, we saw student projects that met that criterion — a remote-controlled lawn mower that will be used by a disabled community member; a courtyard art installation that included kid-friendly percussion instruments tuned to specific pitches and used in school-wide celebrations; and emergency kits and communication plans that would be useful if Atlanta ever has another “Snowpocalypse” the way it did last year. These are the kinds of projects that incorporate deep learning but are also useful, and thus provide kids with a visible way that learning can enrich their lives.

But to work, “project-based learning” needs an investment of time and expertise. When it’s a whim of a pun-loving chemistry teacher, it just squanders students’ learning time.