I have a hard time believing this. I have a grand daughter who hates vegetables and would not choose a salad bar at all.
I do know some kids who hate veggies - but I also know a lot who absolutely would love having a salad bar at school especially if it also had fruit.
If there was a salad bar at school, that could be had without also purchasing everything else on the days menu, my daughter would go for it in a heart beat.
The way it works here is the kids can’t buy a piece of fruit, to get the fruit they have to buy the entire lunch, even if they bring their own.