1) Yes, you need to learn every tense ending as well as every irregular verb to go with it, and you need to learn this off by heart. Honestly it is the most time consuming part of Spanish and therefore causes the most problems in the exam, as well as where the most marks are dropped. No, of course you can forget the odd endings, it won't be the end of the world but you will need lots of tenses for every part of the exam, for example in the speaking the moderator will be listening to hear if you can use a range of tenses appropriately. In the writing exam, it is likely that there will be a grammar section (there was one in our mock, it was out of 10 and I got the highest mark which was 3
) so yeah, different tenses and verb ending will be needed for pretty much every part of the exam, so it is very important that you know and cover as much of them as you can!
2) Our teacher is not foreign, she is English which usually means that she does not speak as fluently as a foreign teacher, but no, she speaks to us pretty much all the time in Spanish, and she has a very good accent and pronunciation, sometimes she makes us speak to each other in Spanish for certain exercises, other wise we get punished such as extra homework/missed break etc. So all in all, yeah, it is important that you speak as much Spanish as you can, and persuade your teacher to as well! At the end of the day, it benefits you all!
3) My current AS class is quite large, around 15 students, which is a nice size to have. It means there are students of various abilities as well as backgrounds. It's very common to have small language classes, but sometimes that can be a good or bad thing, it's all down to the way you feel about it.
I know for a fact that the majority of my classmates/friends are going to drop Spanish after AS, so yeah, I am pretty sure numbers will drop significantly. However, the ones that are going to continue in to A2 are the more advanced students and the ones that are "my competition" in a sense
For me I think it will be better to have a smaller class at A2, as well as a class full of the more advanced students. I just think this because it means I can speak as fluently as I want to them, as well as we can have good detailed conversations (alright, maybe they are not that advanced yet). This is also good for not just me, but for all of us in the A2 class because it means that we can cover the syllabus much quicker and not have to spend so much time on topics and waiting for the others to "catch up". This means at the end of the day, we will have more time to go over the topics and vocabulary that cause us issues, as well as having more teacher attention and focus.
Sorry for the awfully long message
Anything else, just ask