A friend of ours tried to be vegan through her two pregnancies, and the check list of everything you had to eat to get enough protein short of a pound of nuts and multiple soy smoothies was too much - so she cheated and ate cheese.
I worry what happens with those who think supplements and pea powder and wishful thinking are enough to make up for the lack of protein.
In fact adult vegans do cheat every now and then. They just can’t help it because the human body needs some meat. Children don’t have the luxury of that, however; they have to eat only what their parents allow them. I say this from experience of a liberal family member.