Do you think having antibiotics blocks a child's body from learning how to fight against the bacteria naturally?

Sometimes.: That's one of the reasons we don't give antibiotics for all bacterial infections, only for ones likely to cause harm to the child.

Not really: Antibiotics are only of real need or benefit to treat problems the immune system won't fix. You would never omit antibiotics when a meningitis would otherwise kill the kid in days. You might for a middle ear infection that could self heal with immune system help in 6 -8 weeks, but would you really want them to be in pain that long.