Parents need to take responsibility for their off-spring and their own behaviour. If they cannot cook, then learn. There are lots of cookery classes on offer at adult education centres and they are available during the day as well as in the evening. The classes are discounted for those on low or no income and even if they are not discounted, make sacrifices to pay for them.
If you don't or can't attend class, libraries are teeming with cook books so if you can read, just follow the instructions.
Also, parks are free. Children can run round them, kick a ball and generally play. Walking is free too so how about just walking with your child and observing the world around you? You do not need to spend money in order to exercise.
Children only spend about 6 hours a day at school for about 38 weeks in the year. The rest of the time they are with their parents. If a child is obese, the responsibility lies with the parents, not the school imho. Schools can only do so much.
Cut the portion sizes, cut out the snacking, eat nutrious food and spend more time moving. Also, before anyone accuses me of being smug blah, blah, blah, I'm not. The reality is parents can and should do more but too many don't and expect the government/schools to wave a magic wand and hey presto, problem solved.
Take responsibility.