Don't forget content.. if you're aiming to make it 18+ and everybody's in middle school or high school and you specifically say they attend "Anthony Weiner High School" or "Jeffery Katzenberg Middle School", then that content will actually make your disclaimer invalid. Same is true if you mention they look 12 or they were born 14 years ago.. that content will also make your disclaimer false. You have to follow the disclaimer.
No, the disclaimer is for content, which supersedes statements. (The movie "lolita", uses and actual minor, but the sex-scenes are an adult and the "impression" that she is that person, implies it is her. Actual illusions of contact were movie-magic, and acceptable under the protection of the supreme court as "literature art". Just as the bible is, and the TV show, "16 and pregnant", a direct portrayal of minors who have actually "had sex".)
Also, You can be 18 in JR high and up to 21 in high-school.
I could go on, but I dare not.
What is legal, 100% is 18+, in the USA. Anything less, is going into specific gray areas. Also taking note that, "By law, a state/govt approved photo identification is required as a valid 'proof of age', because there is no other legally acceptable way to identify the age of any HUMAN otherwise." Required for the sale of cigarettes, porn, working, alcohol, contracts, paying tickets, entering school.(Thus, there is no, "looks like a minor", because age has no specific look.)
The overruling law, upheld nationally, is "If an artwork reproduction is INDISTINGUISHABLE from reality", then it is against the law. EG, if everyone looking at it, can NOT tell the difference between an actual photograph and the recreation. Which, also has to be an "Identifiable person". (Like Madonna, or Billy-bob-joe down the street.)
The bible depicts minors having sex. At 13 you are an adult, by almost every religion. The courts and even the money used by them, all state, "In God we trust", which includes the writings which depict the God in the first place. (The bibles.)
Without a "government/state approved birth-certificate", the things depicted in the art have no "birth-date", or "human rights", or "identifiable age", other than the age which it was drawn/printed/created... Which would make ALL porn illegal, as it is less than one year old, once made, even if it has adult/non-minors in it.
This is also why a grown man, wearing a diaper, sucking on a teething-ring or bottle, and saying goo-goo-gaa-gaa, in a porn movie, is not counted as "illegal", as it is clearly a "portrayal of child/minor in porn".
Most web-hosts just deny that type of material, as they don't want to be legally bound to protecting it, or those clients.
P.S. Everyone with a "parent" is a "child"... Child is not an age... Use the term "sexual minor", or "underage minor", as there are various types of minors... Laws use those specific terms, because they MUST. (It does not use the term "child", unless it explicitly states above, that the term "child" is referring to an under-age minor, of ___ age.)