I can think of a lot of reasons legitimate reasons why your parents may not have told you. Diabetes or winning the football games are factual events. An IQ test is a snapshot, a number on a given day. That number is one piece of information that absent interpretation doesn't mean a whole lot. Just one thing from your story... If a tester said my kid was "off the charts" I'd question how well they understand and can explain statistical information so I'm not sure I'd want to present anything learned there to a kid at a vulnerable point of life transition.