Finally have my ICF ACC credential and I want to share what worked because the advice I found online before sitting the knowledge assessment was pretty vague. I've been coaching informally for about 4 years but only went through formal coach training in the last 18 months. My training program alone logged 125 hours of coach-specific education.
For the written knowledge assessment, the ICF core competencies framework is the center of everything. I spent about 6 weeks really dissecting all 8 competencies and could articulate not just what they mean but what they look like in practice during a session. Questions give you coaching scenarios and ask what the most appropriate competency-aligned response is - the wrong answers are usually plausible, which is what makes it tricky.
The ethics piece caught a few people in my cohort off guard. It's not just about knowing the code of ethics document but applying it in real situations with competing considerations. I scored 88% overall and I'd say about 30% of the questions were ethics or boundary-related scenarios that required genuine judgment.
Mentor coaching hours were more valuable than I expected for exam prep. Having someone point out where my language wasn't following the competency framework really sharpened my understanding before test day.
The mentor coaching requirement is underrated for the actual exam. My mentor kept catching moments where I'd slip into advising mode instead of coaching mode - that distinction shows up directly in the assessment questions.
Took me 9 weeks of study, about 1.5 hours a day. The practice questions from ICF's own prep materials are more straightforward than the real exam. Don't be fooled by high scores on those.
Currently in the log hours phase, sitting the assessment in about 3 months. The ethics scenario stuff is something I haven't spent enough time on yet - this thread is making me reprioritize.
I failed the first attempt at 67%, passing is 70%. Had to wait 30 days to retake. Second time I focused almost entirely on competencies 4 and 8 because those scenario questions tripped me up most on the first try.