We're just finishing my daughter's 9th grade year too. Learning that some classical schools consider the logic stage 7th through 9th grade helped me relax about pushing her into Rhetoric level studying. Although she has learned her 5 paragaph essay, she's not an arguer! So we continued studying Rennaisance/Reformation/Reason in the last MOH book and while I hoped her reading up to par via exposure. She read the whole LOTR trilogy, plus a Scott O'dell book, Twain's The Prince & The Pauper, The Faerie Queen (the workbook The Grammar of Poetry helped prepare her for this) and we'll finish out the year with Much Ado About Nothing and Part I of Pilgrim's Progress. I'm planning on doing PP the WTM method, and if that goes well we'll head into 10th grade U.S. History ready to design our own literature program. If not, we'll use Lightning Lit, possibly. So, aside from getting the credits issue decided, I think assessing your child's readiness for classical high school is very important for 9th grade and to ease into the subject areas where you may think he may not be ready. DD did Geometry, Latin II, Classical Astronomy, Theology without much problem while she came up to speed in the literature/writing readiness. I feel very comfortable with proceeding with the WTM Rhetoric suggestions at this point, and dd is ready to write her persuasive & research papers.
Another issue is deciding whether you will to "teach to the tests" or take a more "love of learning" approach...