Both the vegan school in California and the vegetarian school in Hertfordshire, England are doing an excellent job.
It's amazing to see schools concerned about sustainability recognising that the meat industry is one of the biggest emitters of greenhouse gas emissions, and that it is bad for the environment in many other ways too.
If they were serving healthy dishes with animal products in, there won't be too much of a health difference, but if the kids are eating loads of meat outside of school already and generally aren't that healthy, then reducing their saturated fat, red and processed meat intake is going to be helpful.