“Simon, share,” I say.

“No, no!” he shouts every time his friend or her 4-year-old sister plays with any toy in our yard.

Where is my easygoing son, usually ready with a hug rather than a scowl? Perhaps I made a parenting error on this September afternoon. I had picked him up from the day care he recently started attending two days a week, and less than an hour later, I expected him to share his toys and his mother.

My neighbor says not to worry. Her 4-year-old prefers solo time after preschool. Simon may just want Mommy-and-me time.

Parents may think the drop-off at preschool or day care is the hardest. The transition home can be even tougher, says Patricia Marquis of Concord, a social worker and early-childhood authority. “You’re picking up a very tired child, because they’ve gone from a home setting to a place with new rules,” Marquis says. “When kids are vulnerable, they tend to be controlling and more rigid.” Creating an after-school routine can help, but more important, take cues from your child, she says.

The next time I pick my son up, I follow his lead. We spend minutes staring at a rabbit that is outside the center. “Bunny. Hop, hop,” he says, then hops and giggles. At home, he plays alone in the sandbox until he spots the 4-year-old next door. He is eager to use her slide, and then happy to let her push him in his red car. This is on his terms.

Simon, after his “school days,” as we call them, often clings more and is more stubborn. He insists on eating from our laps rather than in his booster chair. He is trying to regain some control where he can -- his home -- the most familiar place in his world.

How does your young child handle the school-to-home transition? Next week: How much parental boasting is too much? Last week: Bending the house rules Send comments to magazine@globe.com.