Parents have long debated when exactly young children should start school. Now, Connecticut — one of the few states that still allows 4-year-olds to start kindergarten (provided they turn 5 by the following January) — is considering changing the rules so that kids would have to be 5 by October 1 to start. Many parents, especially well-to-do ones, advocate delaying kindergarten for a year to let kids develop more. Others say the practice is unfair to poorer kids whose families can't afford a fancy preschool while they wait out their kindergarten start date. Should all kids have to be 5 to start kindergarten?

Yes, 4 is too young: It's easy for me to pick out the 4-year-olds in my classes, says Erin Ferrantino, a Connecticut kindergarten teacher, as quoted by The New York Times. They're the kids having a "hard time holding it together." It's a long, "draining" day for 4-year-olds, and they're typically just "not developmentally ready."
"Too young for kindergarten? Tide turning against 4-year-olds"

It should be determined on a case by case basis: "Children vary widely in their development and readiness," says Kristina Chew at Care2. I know school districts are already overburdened with problems, but still, can't we ditch the firm cut-off dates? It would be better for the kids if we could base these decisions on "where each individual child is in terms of their academic, cognitive and social development."
"Should only 5-year-olds enter kindergarten?"

Even 5 can be too young: My 3-year-old son will turn 5 just five days before the cutoff in my state, says Sasha Brown-Worsham at The Stir. If he enters kindergarten at 5, some of the kids in his class would be almost a full year older than him. Because of that, I'm considering not starting him until he's turned 6. "Kindergarten is not what it used to be." It's less about playtime and more about doing real schoolwork at a desk for hours on end. My son may need to wait a year and "develop more self-control" before he's ready for that.
"Should I start my son late to kindergarten?"