I made it from an A2 in French to a B2 in 4 months of full-time study.
Intensive courses. The Alliance Française in Paris has several accelerated, in-person courses that might be worth a look. Here's one for
total beginners and
one that starts at A1. I've never taken either of these courses, but they have 72 hours of class a month, which is a good sign. Also, when considering an intensive French school, ask them how many of their students get a passing grade on the DELF B2 (or a score of at least B2 on the TCF), and how long this typically takes for dedicated students. The nice thing about the DELF B2 is that if you can pass it, you actually have a pretty decent understanding of French. So any school which can reliably produce passing students is probably doing something right.
Self-study. Assimil French or the excellent older
Assimil New French with Ease will get you to A2 in 5 months of consistent study, putting in 20-40 minutes per day. It's reliable and effective. But I've never tried to accelerate it by doing 6 hours per day. Maybe someone here knows a good rhythm for doing that? French in Action had a good reputation once upon a time. The old FSI courses can be a bit brutal, and I don't enjoy them personally, but they absolutely work, and they were designed to be part of a 45 hour/week curriculum. And definely see iguanamon's
post on the "multitrack approach."Once you hit the A2 level, I could offer you lots of advice on moving fast. But one key part of making very rapid progress is having a mix of activities, some of which you focus on when you're fresh, and others which you can do when you're brain-fried. When I was working towards B1 and B2, here was my mix:
- When fresh (2 hours/day). 30 minutes 3x per week conversational practice with a tutor for DELF B2 prep. Writing 50-100 words a day and getting them corrected. Making Anki sentence cards by copying sentences from interesting electronic sources, and looking up stuff I didn't know.
- When fried. Watching Buffy in French. Reading books or online news articles. Listening to French music.
- When standing in line or otherwise waiting. Reviewing Anki cards, 20-40 minutes per day.
Your activities would be different, especially if you're starting from scratch. But the general principle is that you should be spending a
lot of time doing things in French, and that you need to match the intensity of the activity to your energy level. But I always liked Khatzumoto's rule of thumb (paraphrased): "Am you looking at English right now? Listening to English? Then fix that." The secret to moving fast is to put yourself in a position where
learning is the easiest way to thrive. This is why total immersion with people who speak zero English tends to work so well, even if you have no real courses or instruction.
Good luck, and don't hesitate to create a language log and ask questions!