This is absolutely possible!! In fact it is these circumstances that I am under currently. I missed Unit 1/2 due to it clashing with another one of my subjects, so over the summer break I went out and bought the text books my class completed during the year, and completed them over summer. When there was something I didn't understand entirely, I would see if there were any relevant websites (there a multitude of resources available online), if that failed, I turned to certain websites like lang-8. Think of my particular example as a pen pal website (kind of)... let me explain... On the website a Japanese person learning English would post an essay or sentence and someone who had English as their native language would correct/offer advice. This worked hand in hand with those who wear learning Japanese, all my questions were answered by a native!
I have a profound love for second languages, so studying was 'easier' for me, the biggest skills you want to acquire from 1/2 are in my opinion, the ability to have general conversations, and memory retention. Learn a grammar point, study it, revisit it 3 weeks later to keep it fresh! You just have to be prepared to do more than the person sitting next to you, even more so in your case.
Hopefully this offered an insight, it's possible, it's an amazing subject, you just have to work hard