When I began teaching 25 years ago, it was unheard of for a youngster to be placed in time-out at preschool or kindergarten. In fact, I don't even remember that term being used when I earned my credential and did my student teaching. In college classes, our professors drilled in us the importance of “developmentally appropriate practices,” meaning that young children learned best when moving, doing, exploring, talking, interacting, and discovering through their senses.
If there was a behavior issue, we were taught to re-direct the youngsters to another activity. If kids were getting frustrated with one another while playing blocks, for example, we'd say, “it's time to go outside and ride tricycles!” We'd never think to put preschoolers in time-out where they would feel shame and not understand why they were being reprimanded. That would be considered cruel.
Now, when I visit various preschools throughout the year, it's rare when I don't see a child in time-out (almost always a boy and more often than not one of color). They're typically removed from the group for some “horrific” offense like being unable to sit still for a long and boring circle time, not being able to remain silent while the teacher drones on about the calendar and weather, or itching to play with their buddies in the sandbox rather than hearing the teacher read yet another story. The normal behaviors of 4 and 5-year-old children are now seen in our society as disruptive, naughty, and cause for great alarm. While most countries celebrate each stage of a child's development and see no need to rush it, we in the United States want kids to grew up too fast.
In the past 25 years, I've seen a huge decrease in play time at preschool and kindergarten as we push little kids to learn more and more at younger and younger ages. There are more teacher-directed lessons, longer circle times, more paper-pencil tasks, and more rote learning. Preschool is no longer that joyful time to make friends and to develop a love of learning but a means to prepare kids for kindergarten. Most likely, your grandson is the victim of that misguided mentality, and that's why he sits in time-out.
I 'd be concerned that your grandson is getting the message that something is wrong with him when there isn't. The children I see placed in time-out at preschool and kindergarten are typically the brightest ones: curious, independent, and energetic. They get bored easily when the teacher does her spiel, wanting to get up and explore the stimulating environment around them, not just sit and listen.
Your grandson's parents, like so many moms and dads these days, are naively impressed with the early academics now presented in preschool and kindergarten. They see it as a good thing, believing it will give their kids a competitive edge. They're not familiar with the research (Dr. Peter Gray, Dr. Nancy Carlsson-Paige, and the organization, “Defending the Early Years”) that shows the decline of play over the past 50-60 years corresponds to the increasing number of mental health issues in children and teens: depression, anxiety, narcissism, and suicide.
I recommend your grandson switch to a play-based preschool that adheres to developmentally appropriate practices. I'm sick and tired of parents getting the message from preschool teachers that there is something wrong with their children when there absolutely isn't. Unfortunately, preschool teachers are under enormous pressure now to get kids ready for kindergarten: writing their names, knowing their letters and sounds, counting to 100. They're not looking at the bigger picture: getting little children excited about learning and building the belief that learning stems from their own curiosity, not from a teacher.