No matter what you think of school policies on what food students are permitted to bring in, having a junior Stasi force of fellow pupils ready to inspect the sacks looking for contraband is ill considered.
And a more detailed story here:
Why stop there? Once properly trained, send the youngsters home to call out their parents for drug use, or eating ice cream at breakfast, or holding unpopular opinions. They can earn badges for their efforts at informing. You can go all 1984 or Hitler's Youth and give them smart uniforms and armbands to wear as they carry out their duties.
School aged children are learning how the world works, and how to navigate their way through it. I personally feel a bit of healthy suspicion isn't a bad thing, but this sets up a situation where they learn only to fear. Not the best way to form friendships.
I can imagine what the, "Negative comments" directed at the students doing the checking were.