The Question Isn't Readiness. It's What This Year Is Doing for Your Child.
A three or four year old doesn't need to pass a readiness test before starting preschool. What they need is a place where this specific year of their life is being used well. If your child spends their days somewhere safe and supervised, with meals on time and a nap that happens, it can still feel like enough. Nothing looks wrong. But nothing is being built either.
This is the age when a child learns to sit with a task that's a little hard instead of giving up on it, to work near other kids without a meltdown, to hold a pencil, to follow two step directions, to ask a question instead of freezing. None of that arrives automatically at kindergarten. It gets practiced, daily, at exactly this age. A child who spends a year in an unstructured setting isn't behind in any way you can see yet. The gap shows up later, when classmates who practiced these things for a year walk in already comfortable with them.
So the real question isn't "is my child ready." It's "is this year building something, or just passing."