I've seen how school lunches are made everyday. In the USA, a calendar is sent out to every family in the district with the lunch menu for the month. So, the lunch menu is always well publicized ahead of time. Sometimes the school lunches don't include meat for that day for example such as cheese pizza. Every morning, cooks will come to the school district headquarters and mass cook the lunch for that day for every child in the school district even if that child does not eat school lunch. After the food is made, the food is packed onto trucks and sent to every school in the school district. At the school, lunch staff will heat up the food and get it ready for the kids. Allergies are accommodated, but that has to be dealt with on a school by school level usually with the assistance of the school social worker to collaborate with the family and not on the district level. In middle school and high school, there are usually 3 to 4 options for lunch that kids can pick everyday including a vegetarian option. In middle school, I decided I didn't want to eat meat during school for some reason, so I almost always ate a vegetarian lunch during school. I remember eating peanut butter and jelly sandwiches or a garden salad with my choice of dressing. Basically, school lunches are mass produced for all of the kids in the entire school district. Because many kids are on free or reduced lunches, the school district needs to make these lunches as cost effective as possible while also following federal nutrition guidelines. It is not cost efficient to have non-halal meat used for some of the meals and halal meat for others when the meals are being mass produced. Also, halal meat is more expensive than non-halal meat. When the school district is trying to make sure every kid in the school district has a lunch even if they don't eat it while acknowledging that a certain portion of students are on free or reduced lunches, the logistics need to work out.