OP, please try to ignore the PP's who don't even rad your post properly.
They are making inappropriate comments based on only half reading what you said.
It's too many years since my child was of school age, let alone 7 years of age, so obviously schools policies have evolved.
Yes I agree what ever should be signed, you should sign.
Tho it feels pointless if you can sign without even performing the exercise.
Your 7 year of is NOT responsible for reminding you to sign, because in some households, such a reminder from a child could be treated as the child being cheeky to the parent, and at risk of being punished.
There seem to me, an awful lot of scenarios where something fails to get signed, and I can't see a case where the child (especially one so young) should receive a punishment such as your child received.
It feels as tho if that action was to carry on through life, a person could go to prison because the chap down the road broke the law...
Even if it is a punitive offence, for your child to lose a whole 30 minute break, is way over the top.
If as others have said, he acted inappropriately or abusively, then of course an appropriate punishment is due.
I've not a clue how you go about amending this situation, but I'm just giving you my opinion... and I agree the child should NOT receive punishment for the forgetfulness of the parent.
You can in future, (now that you know) set an alarm up to sign whatever, or you could sign in advance.
It's almost laughable.
I can really see why you're aggrieved.
I also see that the school may be overstretched, but that's hardly your child's fault either.
I feel pretty upset for you.
Good luck going forward.