Not a single state received a “B” or an “A.” New Jersey, Ohio, Iowa, and Minnesota were the only states to receive a “C” grade.
Hooray for my home state of Ohio...I guess? (if mediocrity is something to aspire to?)
I guess I'll give my buy-in on each of the 4 criteria:
child marriage -
I guess I didn't realize that this was a thing that was going on prevelently... However, based on the standard they've set (which seems to surround officially codified law explicitly setting an age of 18), it would seem that there's a difference between "not having an explicit law for it" and "it actually being practiced". For instance, California and Washington State are among the states that fall into that category, but are child marriages a thing being practiced in either of those two places? Or is it just a case where they don't have an explicit law for it (but have other laws that would make the concern moot)?
I would also point to other conflicting laws on other matters relating to sex that would make a "no marriage until 18" tricky to enforce consistently. For instance, the age of consent, the age at which a person can get an abortion without parental consent, the age to make medical decisions without parental consent, etc... could make it tricky to make a "no marriage until 18" cohesive with the rest of the policy prescriptions.
corporal punishment -
This one I see as cut and dry, this flowchart sums it up
(this answer will undoubtedly lead to an influx of anecdotes about how "My parents spanked me, and I turned out fine!" by people who have pent up aggression and see violence as the answer to problems)
child labor -
This one I would question...it seems to rest upon whether or not a state has laws dictating the minimum ages for labor within certain sectors. A lot of the "qualification" on this would really come down to an individual level based on the maturity and physical development of the minor. For instance, they mention at a minimum age for the agriculture sector of 15. I feel like that's unreasonable for someone growing up in a "family farm" environment. 13-15 is an age with a lot of variation in terms of physical development. You have some "farm boys" who are in 8th grade who could operate a tractor, bale hay, and handle farm animals better than most adults in the US, and you have others in that age range who would look like little kids. In an age range with so much variation, setting one particular number seems arbitrary.
juvenile justice -
This one is another cut and dry one...set an age, and either you're an adult or you not at that age. "Having it both ways" is impractical.
Trying someone as an adult, not based on their age, but based on how bad the crime was is a bastardization of justice and serves no other purpose than to satisfy the vengeance-lust of the victim. If at 15 you can't buy a cigar, can't buy a beer, but can be tried as an adult for a crime, then the state needs to "show their work" with regards to how they came up with that cockamamie system. The fact that we have different ages for different things (as opposed to many other countries who have set one single age for "adulthood") is indicative of a problem.