I think that PE in school should not be compulsory because year 12 and 13's do not have to do it and they have free periods when years 10 and 11's do not. I think it should be an option so you say whether you would like to do it or not and then if you do then great but the ones who don't want to do it have a free period to do extra work/study. I understand if that school specialised in PE but mine does not and we never do anything in PE worth while and it causes you to be late for the next lesson after it so you miss actual academic work.
some people who don't exercise are not obese they just eat a normal balanced diet with all of the necessary things like 5 a day. This will increase their metabolic rate so they don't store unwanted fats. Plus a lot of children/ teenagers feel self conscious in PE because they don't have any athletic ability so to them its embarrassing with everyone around them being so good at it. Also at the end of the day the more time you spend doing actual academic work the better because intelligence will let a lifetime but your athletic ability will not, so what's the point.