It is never too late to start homeschooling
You'll probably need to file a "letter of intent" with the school board, and depending on your state, there may be a few other requirements such as record-keeping and/or testing, but you should be able to start homeschooling right now.
The first thing to do is get your hands on a copy of the syllabuses for each course you were taking, and if possible, some textbooks as well. A number of schools offer home learning programs, and while this isn't strictly considered homeschooling, it may be your best option right now - or you can see if they will let you borrow some books, or buy used copies at a reduced price.
Short of this, you can buy a grade's worth of curriculum from one of the major homeschool suppliers and work through the parts you haven't covered yet.
http://www.home-school.com/mall/curriculum/general.html
http://www.home-school.com/mall/
It's probably best to go with a curriculum that lets you pick your level for each subject, since what the school covers in x grade may not be exactly the same as what a packaged curriculum covers, and your objective here is to be ready for the next school grade.
And keep in mind that you don't have to cram everything into the rest of the school year! You can spread things out over the summer as necessary, so long as you finish everything by the start of the next school year. I always advocate working year-round anyway, since you can cover more material in less time per day that way, leaving your days mostly open for extracurriculars and the subjects you enjoy.