A child does not have his parental feild trip form and wants to get on the bus for the outing. He insists his dada said he coudld go. It is time for the bus to leave, what do you do?
What is your ethical responsibility?
To the child, parent, school
The school should call the parents to obtain verbal permission or even better, to drop off the signed form at school. Delaying the bus for a few minutes wouldn't cause a major hardship for the school or the children.
If they can't obtain permission, then the school should not allow this child to go on the field trip. This protects the school and assumes that if the parent had wanted the child to go, then he would have returned the signed form.
As far as the child, the school must act in loco parentis, that is "in place of the parent." Since it doesn't have a signed permission slip and the child is obviously too young to make decisions for himself, then the school is obligated to keep him at school. Hopefully, the administration can provide the child with an entertaining day if they can't get the parents to pick him up after the bus leaves.
By the way, the value of a signed parental field trip form is of doubtful legal value. Some schools might take a chance and let the child go on the field trip -- even without a permission slip. But I don't think that's the ethical decision.