Age of majority
Don't you think that the age of majority being 18 and in some countries even 21 is way too high? I mean, throughout the whole millenia, leaving your childhood meant your entering adulthood, there was nothing in-between. The fact people in their early teens start to feel more adult, regardless of whether they really are adult people mentally (which is rare in case of younger teens unlike it happens with older teens) or whether all adult things they do is drinking, smoking etc. is caused by the fact of the changes in their brain - they suddenly get the possibility of performing all thought operations available for adults. Neverheless regardless of the maturity level of such a young person, a teen can't fully decide about themselves until they are 18 or 16 - depending on the country they live in.
And here is what I mean: what if a person able to support themselves earlier could be given all the rights of adulthood on this condition that they would get evaluated by a psychologist and if they decided the teen is already mentally at least, an adult like any other adults, they could get all the rights reserved for adults. Like a young movie star/model/teen writer/whoever who has money to live on their own and needs to be able to decide about themselves. What do you think? After all, history knows many teenage kings, scientists etc. I read once in a discussion about a girl of 14 who was pregnant that "she needed as many help as possible if she decided to keep the baby because otherwise she just wouldn't be able to deal with them on her own - just as well you could expect from her being a housewife and taking care of a family of three". As if it wasn't quite a normal thing throughout the whole history of humanity and as if this history didn't know kings her age. If it depended on me, the age of adulthood would be 16 and it would be possible to get the rights of adulthhod earlier in some cases.