I understand the headroom concept in general (i.e. in particular the spelling percentile)...clearly this is not a great test to differentiate between 93%, 95%, 99% etc....also my son is a normal age for the 1st grade (7 years, 2 months at time of test)....but the juxtaposition of the total battery percentiles against the component percentiles still does not make sense.
Let's take these test percentiles and place them into an example: a hypothetical modified "decathalon", with 5 events, and 100 athletes...my son gets the highest vault, first place in the pole vault (i.e. 99% as he appeared to do in math), then the 2nd place, 2nd longest in the javelin (i.e. 98% as he appeared to do in reading). Let's say the last 3 events are simple pass/fail tests: drink a bottle of gatorade, eat a protein bar, and eat a bowl of wheaties, and that all 100 athletes complete the last 3 events without issue. If you summed up the results of all 5 events, my son's score should still place him no lower than 2nd place (98%) in the total battery of events, right? The percentiles given to me in the Stanford 10 achievement score sheet do not have that same mathematical logic, leading me to assume that either the component percentiles or the total percentile or both are not true percentiles.
