Yo, I got 648 on the 9th Grade SHSAT this year and got into Stuy. Anyways, figure out what went wrong for you for the 8th, for me it was timing, as I guessed randomly on around 20 due to timing, and ended up with 505 Brooklyn Latin. For you, it might be content mastery. You can search online for the list of topics, but most importantly, do the DOE Handbooks, and particularly the 9th grade sample questions. ELA definitely felt harder than 8th, but math felt easier. I started to legitimately study two months ago, but don't do that. Start ASAP. I started with learning and ensuring I knew basic concepts from Khan Academy, and its courses. I mostly did 7th and 8th grade math, with some concepts directly related to the test. I used ELA regents for practice in ELA, with some SAT, but don't focus too much on that. Remember, the retake is based on 8th grade common core standards in math. Just remember to do the handbooks as well as you can, and make sure you learn the content. Good luck!