Sorry..I feel absolutely the opposite. You don't get to pick and choose the rules and policies you follow when you choose to enroll your child in a school..especially a public one. You either follow the policies set forth or you don't send your child there. By all means..advocate for change via the proper channels but things like truancy are generally outside the hands of the school and are laws set forth by the state or county you live in so your fight would be with them.
Federal law says every child is entitled to a free, appropriate public education. It says nothing about the parent agreeing to follow the policies and procedures set forth by the local education agency with regard to supplying doctor's notes for every absence. Such notes are arbitrary requirements and not necessary for the school district to continue its job of educating children. Let's be honest, not every illness requires a trip to the doctor, but that doesn't mean your child is well enough to be in school. It is better that they are home instead of spreading their germs throughout the rest of the school.
School districts have the right to set policy and everyone has the right to choose not to use the schools by homeschooling or finding a private school. I agree with those who say that you can't just pick and choose which rules to follow.
My opinion differs somewhat. A school district has the right to set
reasonable policies. As parents, we have the right to choose whether or not to comply with those policies. However, if we choose to not follow the policies set by the school district, we need to be prepared to deal with the consequences of our choices, which may include advocating for a change to those policies.
As for the OP, she was aware of the basic policy regarding absenteeism. However, the school decided to add to the policy, at the end of the school year, retroactive to the beginning of the year, by asking for details regarding her child's absences. That's like changing the rules in the middle of the game and that's not acceptable.
It shocks me that people believe they have to follow such ridiculous and unrealistic policies just because they are set forth by a group of bureaucrats who think they know how to parent your child better than you do.