Chances are, those tests you took in school were actually achievement tests. Certainly that's true of the classroom testing, as IQ tests tend to be administered individually. And yes, the norming populations are skewed: norming, particularly in the '50s and '60s and likely into the '70s, was done on students in university lab schools (often professors' kids), private schools, and the public schools in the "nicer" neighborhoods.

During some evaluations, I was given the WAIS-R (Wechsler Adult Intelligence Scale-Revised). The results: 99th percentile, which means I outperformed 99% of the norming population. What does it prove? That I did well on the subtests. Its bearing on my current reality? None whatsoever.