There is really no reason to fail any tests in API. I'm not the sharpest tool in the shed (my ACT score was 21, SAT of 900) and i basically crawled out of high school. However, i didn't fail a single test in API and all it took was some good studying. The info is, for the most part, not really important later, but you do have to know it then. Everybody i knew who failed more than one test never studied hard and tended to party too much. Your job is to study and the stuff isn't hard. if you can graduate college, you should have no difficulties in API.
That said, i know things are more stringent now than when i went through. Tell your buddy, or anyone you know who hasn't done well in API, it does matter, not a lot, but it does, especially now. If your buddy has a hickup later in training they can review your API grades and i understand they're not terribly sympathetic to people not doing well in API. If i were an IP on a TRB and i saw that the stud in question had more than one API failure, i'd take that into consideration (if the reason for the TRB were academic).
Build those study habits in API as the testing methods are more or less the same in the Navy thereafter. For four weeks of API if beer doesn't touch your lips but you pass every test, i call that above average headwork.