As much as parents want to complain, teachers/administrators do too! They want the kids to run around and burn up some pent up energy. They know kids need to blow off steam and the value of recess. I volunteer on the playground sometimes and unfortunately there really is no choice on rainy days. Those kids would be bitching and moaning, at large percentage would not have the appropriate outdoor gear, and they would be miserable the rest of the day with their wet shoes, hair, clothes, etc.
With 220+ kids at recess at a time, there is no indoor place for them to run around and the kids play in the rooms instead (2 classes per room).
If you are so concerned about your kids getting out on rainy or snowy days, then you spend the afternoon with them outside once they come home from school. Don't expect the school to do what you wouldn't do yourself. BTW, you can always check your child out for recess and take him/her to a park if you'd like

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