Should the minimum age for marriage be lowered?

HenLaoLaoShi (Expat in China)

During my time as a high school teacher here in China, I met a lot of 18-year-old kids. I have met few that seem even remotely ready for marriage. On the other side of the equation, many minority kids in the mountains here get married before they reach 18. However, in the case of poor rural families, the girls already know their life plan is to work until their parents choose a mate, get married, have a few kids, and work until they die. I see no real benefit in lowering the legal marriage age.