Oregon does have a bicycle helmet law that requires bicycle riders 16 and under to wear a helmet while riding a bike. While I do see many 16 and unders wearing helmets, I do see many that do not.
This blog is about what adults are teaching children, not what the law says. Bicycle helmets are proven to protect the head in accidents. New York City has statistics. (Almost three-quarters of fatal crashes (74%) involved a head injury. Nearly all bicyclists who died (97%) were not wearing a helmet.)
I would like to point out that if you are trying to teach your child bicycle safety and require them to wear helmets, and you do not wear a helmet, you are being hypocritical. Let's face it, if you are not wearing a helmet, but expect your children to do so, they see through your hypocrisy. Please do not expect your children to acquire a lifelong safety skill if you do not show that you embrace said skill.
If you want your children to do the right thing, you must demonstrate the right thing. Otherwise, what are you teaching your children?