The thing is, it is unreasonable to ask the school to provide all the outdoor play, all the sport and all the socialisation, as well as all the education, that they receive in a week.
For the sake of argument, a primary child might be up and around for 13 hours per day - 91 hours per week. They are in school for about 6.5 hours, 5 days per week, a total of 32.5 hours. Of those 32.5 hours, at least 5 are spent in unstructured outdoor play (lunch and playtimes), and 2 in PE (in EYFS and early KS1, the amount of unstructured or structured play is much higher).
So a primary age child spends around 36% of their waling hours in school in term time.
Of those hours, at least 7, so over 20% of the time, is already spent in sport / play.
Is it reasonable to reduce the amount of time spent on non-sport / activity parts of education further, despite the fact that children have nearly two thirds of their waking hours outside school? Is it reasonable that NONE of those outside school hours are spent physically active?