punished for eating nonveg food at school

I study in an aided government school by the agamananda swamis. im 17(+2 student) and my sister is 12(7th student). Recently while I was talking to her I came to know that the school doesn't allow non veg food. Both my parents are working and have to leave by 8:30 so on most days I have eggs and rice for lunch and my sister eats the lunch provided at school. She hated the food there so one day my mom gave her chicken. The teachers *caught* her eating chicken and took her to the principals office. There are students/leaders who are appointed to check if a student brings non veg food.She wasn't allowed to eat the chicken that day and ate plain rice.She also told me that they werent allowed to eat the eggs given by the school at school and had to wait till evening while all the kids who chose the milk/banana could you drink/eat it there. Im confused on how a school can control what a person eats as long as we dont dispose any waste there. I used to study in a CBSE school so please educate me if I'm wrong. Btw none of this no non veg shit was informed when joining the school