I agree with Mike-san. I don't know anybody that has passed the JLPTN1 in just a couple of years by following a classroom curriculum, people that pass quickly do it with a lot of independent study. (They may also take classes or having tutoring sessions, but mostly, they put the hours in on their own.)
Once you have the basics down, I think it's quite important to do a lot of reading and listening to actual native materials. Simply reading all of the material in the time the test allows becomes difficult at the higher levels. Essays are the best practice material because the majority of the reading selections are essays. (There is always at least one reading that looks like a notice of some kind - an advertisement or a train schedule change, something along those lines where you have to pull out practical information.)
The spoken dialogues are usually some kind of school or workplace discussion about some decision that needs to be made for an upcoming event (what to buy a co-worker for their birthday; getting advice from a teacher about how to organize a group presentation; that sort of thing.)
Useful places to practice for free are,
Japanese travel - Learn Japanese Online - JOI Teachers blog
WEB版 エリンが挑戦!にほんごできます。|Global Home
NEWS WEB EASY (and of course the regular news too when you can).
NHK高校講座 (reading the pdf before listening to or watching a lesson makes it much easier to understand what's going on, and provides good reading practice. Reading the pdf after makes more challenging listening practice followed by a check of your comprehension. ベーシック国語 was pretty good practice for me, 世界史、日本史 and 社会情報 should be good too. The science and math classes are probably not as good for practicing for the JLPT, but if you feel like you need to review a particular subject to do well in school then you could double-up on practicing Japanese and studying for school by choosing one of those.)
I never used them, but many people do get the Kanzen Master books to prepare for the JLPT. There would be a lot of duplication with your current course so maybe you wouldn't want 文法、語彙 or 漢字, but the 読解 and 聴解 books will provide very precisely targeted reading and listening practice. You can probably find used copies if price is an issue, it's a very popular series.
Amazon product ASIN 4883195724