What do American public schools do if you don't have a doctor's note every time your kid is home sick?

Edit: I forgot the old internet rule of having to define every parameter of a post clearly or else people will bring out the most extreme situation.

So here's the parameters: Normal childhood illnesses like strep, ear infections, bronchitis, etc. Illnesses that can normally, unless complications arise, be treated at home. Not chronic conditions that require regular hospitalizations. Not serious medical conditions. Not conditions that merit a 504.

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Been reading some parent posts on social media and quite a few parents are saying they take their kids to the doctor for simple things like colds because their school requires doctor's notes for absences.

I understand private schools can kick out kids for any reason, and chronic medical conditions can cause excessive absences schools are concerned about, but has anyone faced repercussions for their kid in public school having too many regular kid illness sick days? What is the school going to do? They can't kick the kid out. Call CPS, who will immediately close the case after confirming there's nothing wrong with a kid who catches germs? Kick the kid off a sports team when they have an otherwise shining record? I don't get the fear people have when they tell school admin they weren't going to take child to the doctor when the doctor was going to say stay home and rest. Notes aren't required where I live.