As ever, schools can't win either way. I used to cover lunchtimes when we were short of MDSAs and honestly, you'll get parents who moan that we haven't ensured their child has eaten enough and others who moan that their child ate the whole lunch and then didn't have time to go out to play!
Some lunchboxes were huge! Way more than I'd eat and yet some children were told by their parent/carer to eat it all. Poor things!
You then get the children who eat painfully slowly but are hungry enough to want to eat it all. So what should we do? Tell them they can't eat it all because otherwise they won't get any fresh air, or allow them to sit for ages nibbling like a snail?
We sometimes suggested to send a packed lunch in if the child didn't like the school dinners but that obviously didn't usually go down too well because the school dinners are free. (Infant school)
At my school, school dinner children would have to put their hand up before they could eat pudding and we'd see how they'd got on with the main part. Sometimes we'd make a fun game of trying to encourage to eat a bit more veg or whatever but they were never forced!
Similarly, packed lunch children were encouraged to eat some of their sandwich or whatever before they ate their crisps or chocolate bar etc. Surely that's what your average parent would do at home?
There's a middle ground between policing every morsel of food eaten and encouraging children to eat enough food so they aren't tired for the afternoon learning session.
But as with most aspects of school, we simply can't please all of the parents all of the time!