I never said that what she is doing is against the rules. It is perfectly legal to have a 19 year old competing in HS.
It is however important to compare what she is achieving to other 19 year olds rather than limiting it to just HS kids.
Natalie should not be penalized for being a 19 year old in HS but Sarah Disanza running 15:20 as a 19 year old should not be penalized for being a sophomore in College.
Age is a better comparison than education level