Y13 student at LAE
Yes you can leave during break, lunch and any free periods you have.
Teachers are incredibly supportive of less able pupils. They host many drop in sessions after school and generally love answering questions you have randomly during break or lunch. It should be noted that at the end of Y12 if you don't achieve 3Cs you will probably be kicked out. There are so many opportunities to get support that if you still perform that poorly they kick you out (other than in extreme circumstances).
As for your part time job, I know a few people who also balance part time jobs with education. However it requires a certain type of person who is more organised and able to juggle responsibilities. It's certainly possible, but be ready to drop the job if it's too much.
In terms of the general atmosphere, it's just normal. People hang out in the Agora/Canteen sofas and play cards, it's lively and loud in there. There's a community of people who chill in the library. Its the type of environment where people might just come up to you and ask what you are reading, leading to engaging and satisfying conversation. In lessons I love asking questions and I'm always somewhat excited, happy and certainly loud. This is not seen as nerdy and I've never felt out place. Since our headmaster put up the great map showing where last year's cohort went to university, there's often a small group of people just looking at it and thinking about where they may sit on that map in the future. During exam and university application season the library gets fuller. People love helping each other out and I often see people working on personal statements together, or answering questions. I will be sitting a university entrance exam, and when I've hit a wall with a hard past paper question, I can freely walk into a available maths teachers class, or just ask somebody nearby if they would like to help me with a challenging question. Unless they are busy, people are fine. The librarian is also great. If you want to order a book she will do so on your behalf, and mail you when it arrives. There's a wide range of sports and clubs available including things like Feminist society and debating to student investor challenge, chess, drama and Excel Club.
The greatest asset is the teaching. Staff always have a relevant degree and experience in the subject they teach. We have Economics teachers who were post hedge fund managers, and most teachers have gone to top universities if not Oxbridge. If you ever want inspiration, degree ideas or life lessons they will happily provide. Staff are generally very young and fairly fresh from university. However the teacher selection process only lets in the great staff.
I love it here!
I also considered the exact same colleges you have. LSC and NewVic are fundamentally different to the top tier academic sixth forms that make up the rest of your list. From looking at the colleges during open days I concluded that LAE was the most enriching environment and I'm glad I am here.