What age is respectable to be married at?

For example, is it reckless to get married once you’ve graduated from high school, even if you’ve been with the same person for 3–4 years? Is it reckless to get married before graduating from college? I’m not asking about the steady-ness of the relationship, so just assume people involved are as in love as they ever could be. The old ‘standard’ used to be could you provide for your family, but it seems like that’s faded since people are getting married before grad school/when they don’t have a secure job yet.

Thoughts?