“He doesn’t have attention deficit,” I said. “We’re not going to medicate him.”

The teacher looked horrified. “We would never suggest you do that,” she said, despite doing just that in her previous breath. “We aren’t even allowed by law to suggest that. Just get him evaluated.”

And so it began.

Like the teachers, we didn’t want Will to “fall through the cracks.” But what I’ve found is that once you start looking for a problem, someone’s going to find one, and attention deficit has become the go-to diagnosis, increasing by an average of 5.5 percent a year between 2003 and 2007, according to the Centers for Disease Control and Prevention. As of 2010, according to the National Health Interview Survey, 8.4 percent, or 5.2 million children, between the ages of 3 and 17 had been given diagnoses of attention deficit hyperactivity disorder.

What I didn’t know at the time is that there’s no clinical test for it: doctors make diagnoses based on subjective impressions from a series of interviews and questionnaires. Now, in retrospect, I understand why the statistics are so high.

We made an appointment with a psychiatrist on the Upper East Side of Manhattan. After we filled out an extensive questionnaire, she did the interviews and had Will’s teachers fill out short behavior questionnaires, called Conners rating scales, which assess things like “squirminess” on a scale of one to five. In many cases, I discovered, diagnoses hinge on the teachers’ responses.

A few weeks later we heard back. Will had been given a diagnosis of inattentive-type A.D.H.D. It was explained to us this way: Some children who are otherwise focused (Will had been engaged during his interview), have a hard time focusing in “distracting situations” — in Will’s case, school. The doctor prescribed methylphenidate, a generic form of Ritalin. It was not to be taken at home, or on weekends, or vacations. He didn’t need to be medicated for regular life.