Milk alternatives don't have any benefits in children. Milk drinking in children is thought to induce growth. You can't overdo it though as it interferes with iron absorption. https://www.nature.com/articles/s41598-020-63647-8 see the references height difference found: https://academic.oup.com/ajcn/article/106/2/597/4557638 may be related to IGF-1: https://www.nature.com/articles/1601948
Do we need big kids? Milk has a ton of calories and could be contributing to childhood obesity: https://nutritionfacts.org/2017/03/16/how-milk-may-contribut...
So replacing it will not change anything in that regard, we just must be aware that (any) milk is (liquid) food and not a drink. Same problem as with softdrinks or fruit juices.
Anecdata: I regularly drank (cow) milk as a child and now I'm over 2 meters in height. But of course correlation with n=1 is not causation, and I'm sure many people here are equally large without a drop of milk. :D