Waiting to eat after a very high blood sugar

I am wondering how long should a meal be delayed if a blood sugar is very high (250 to 300). Lately the biggest problem we are experiencing with my 11 yr old "type 1" son is every time he is really really hungry, he checks his b.s. and it ends up being too high to eat.  He has had many emotional breakdowns because of this and it is heartbreaking to see. We try so hard to manage his diabetes, but are so frustrated.  His last A1c was 7.1, but I would like to do better. It's such a struggle as almost everyday we see a 300 b.s. at some point of the day. If anyone has any advice, I would love to hear it!