From Wikipedia:
"The School of Hard Knocks is an idiomatic phrase meaning the (sometimes painful) education one gets from life, often contrasted with formal education. It is a phrase which is most typically used by a person to claim a level of wisdom imparted by life experience, which they consider at least equal in merit to academic knowledge. It is a response that may be given when someone is asked about their education, especially if they do not have an extensive formal education but feel they have work/life experience that should be valued instead. It may also be used facetiously to suggest that formal education is not of practical value compared to work experience. In the UK, the phrases University of Life and School of Hard Knocks may be used interchangeably."
Yeap... so... "Have not Graduated Highschool" is definitely an applicable option. Everyone takes their hard knocks... some do so with education, some don't. Some people have to work for their education, and some have it handed to them on a silver platter with a trust fund on top. However, in regards to advertisers, this question is about one's level of formal education... and I think those that are actually interested and care about one's level of formal education, are not going to be interested in flippant or facetious remarks.
It's really a matter of audience, and the audience that really even gives a crapola about the answers to this poll, probably doesn't want to have their personal values crapped on as an answer.
Without it even being phrased flippantly - such as "school of hard knocks"... Even if it were phrased as a poll option of "I don't believe in formal education." Would still be an unappealing affront to someone who is examining and cares about formal education level. I don't see any need to be unnecessarily confrontational in constructing a poll (which I'm trying to word in as sterile a fashion as possible). Polling questions usually have to be phrased very carefully to get accurate data, or with a goal in mind. I usually like to try and balance between a goal and getting accurate data.