Minimum age for alt-credit attainment?

[studyingfortests]

Hi,

Does anyone know if there's a minimum age for use of sites like SDC, Sophia, Straighterline, etc?  I have a friend with an extremely precocious child who is interested in taking some classes over the summer (college credit is nice but not crucial.)

I took a quick look at Sophia's TOS and could not see any mention of age requirements.  I know she would not be able to get admitted to many colleges until 18 or 20, but could she earn alt credits between now and then?