I actually know quite a lot about IQ tests. They aren't useless, but they do have a track record of being used to harm already disadvantaged groups.

The original test that some Frenchman was asked to create was not intended to measure intelligence. It was intended to measure school readiness of children of indeterminate age. In the era in question, city kids in France tended to have birth certificates and to also have plenty of familiarity with things involved in school readiness. Their ages could have been used to determine school readiness.

The problem was the rural children of that era often lacked birth certificates and also lacked experience with things like pre-school. They had more trouble fitting in at school already due to coming from a different background than the city kids.

This test then became the inspiration for IQ tests.

Feynman supposedly did not have a very high IQ. Some IQ test he took placed his IQ around 129, iirc. Yet he was widely regarded as a genius.

When I was actively involved in an organization that concerned itself with gifted education, I very often said that "tests are merely a tool." I have heard too many stories of young gifted kids who could not answer a question on a test because it was a multiple answer question and their rich understanding of the world meant that none of the answers fit.

A good example is "Who discovered America?" An average kid may know to correctly spit back the answer "Columbus" because we memorize that in school. A bright kid may answer such a question with something like "Well, it wasn't called America until x date after Amerigo Vespucci came here and before Columbus, the Vikings had settlements here and Columbus thought he discovered India, not a new continent...(blather on some more)...um, what was the question?"

Bright kids can be very hard to properly test. IQ tests are useful tools for trained professionals, but often don't stand well on their own. Furthermore, the last I was keeping up with such info, they were having trouble finding a new test with a high ceiling. The one test previously known to have a high ceiling was getting rather out of date and nothing new was being developed. It was a very serious problem and some professionals were resorting to using the out of date test as the least worst option available.

Most tests ceiling out around 130 or 145. So if you score anywhere near that, you can generally assume that is a minimum IQ. It is quite hard to find accurate tests for IQs above that IQ range and that only goes out 2 or 3 standard deviations above the norm.

I am homeless. I was one of the top 3 students of my graduating high school class and I have had a class on homeless and public policy from SFSU. My IQ is absolutely not 80.

In 5.5 years on the street, I have run into a lot of homeless people. They often do have mental health issues, but they aren't typically mentally retarded, which is your assertion. Homelessness tends to grow out of serious personal problems, such as mental health issues, medical issues and other special needs.

In my 5.5 years as a homeless person, I do very often run into people who are mentally retarded. They are typically in a group that shows up at whatever library or public park I am frequenting and they apparently come from some kind of group home.

There may be mentally retarded people on the street. But I have zero reason to believe that it is the norm or that it explains homelessness.