How long does it take for British Council language assistants to find out their assigned schools?

I went to France, not Spain, but I didn't find out until late August. I don't know of anyone who found out later than August. It's generally easier to find accommodation when you're there anyway, actually being able to see the house/flat in person is invaluable!

You should find out sometime in August. If you're really worried you can usually check with the British Council or the Spanish Ministry of Education, Culture and Sport via email, telephone or Twitter (which tends to get a fast response). I was really worried before my year abroad because I heard very little from my school before I arrived. Don't expect to hear back immediately, especially if you contact them during the summer holidays. If they don't tell you everything you need to know, don't worry, it will be sorted when you arrive.

I was placed in Germany, and I think I found out in late July before the training course started in late August - I'm sure you'll have heard by now, and best of luck! It's a fab experience, make sure you make the most of it :)