I have a Mom friend, whoes kids are now in college, but when they were in kindergarten they had "food" issues, and also needed naps. Kindergarten was full day at our local catholic school back then. So she requested a half day accomodation. The school never answered the request one way or another. So on the third week of kindergarten she sent her son. (Please note this Mom is a graduate of the school.) Then at 11:30 she just showed up to pick him up. She did this for three or four days, and then someone finally said she couldn't keep doing this. She said, now you are finally giving me an answer to my request! Can I get it in writting? They then backed off and gave her permission to do it everyday.
My suggested is this:
1. write a note to the Principal, and ask for a reply in 10 days (cc the teachers) If you can get a note from your pediatrician supporting your claim include a copy.
2. While your waiting for a reply, show up every day at roughly the same time, with as many Mom as you can, and bring your child a snack. (Claim your there for a "doctor" appointment. Take him outside do the snack and then return him.) For Mom's that work, send in a note so a non-working Mom who agrees to help can have permission to take your child to the "doctors appointment."
3. If the 10 days lapses and you have no reply, or the answer is no. Write directly to the superintended, and "cc" the school board. Sending copies of what you sent to the teachers and any reply you recieved. Include a list or number count of all the parents who have started showing up to give their child snack. In this letter stated that you are formally requesting a 504 plan (This refers to section 504 of the Rehabilitiation Act of 1975, it will cause the school stress if you say this.) for you son, because "going this long without food impairs his ability to learn."
4. While you keep going and giving him snack (or maybe stage a "sick day" and have a bunch of Mom's keep their kid home on the same day). They may try to stop you, but you have every right to pick your child up in the middle of the day, particularly if you have the doctor's note supporting his need for a snack.
5. I would also consider contacting a local news outlet, the newspaper, TV or radio, and inviting them to join you all for snack. The school will not like the negative publicity. Also the reporter could call the school to get their side of the problem, which will get someone's attention.
Good Luck! You are very right about the need for snack, and if you don't fight for it, it will be a matter of time before the school will try to say your son has ADHD because he cannot pay attention and do his work. The guy is just hungry. Good Luck!