Hey, I am a few years older than you.... and I went back on the 3rd of September... the first day is always one of the worst. Like you, some of my friends left and I didn't really know anyone in 3 of my classes, but now I am meeting some new people and it is fine. You should get used to it and feel a bit better about it in a few days once you get used to being back

As for teachers, I had a really bad maths teacher a few years ago (I no longer do maths.. I am in what we call 6th form here, so I only do 4 subjects now) who was quite horrible actually... he made a little 11 year old in one of his classes cry (we were waiting for lesson and saw her run out) and then he laughed about it... but I made it through 2 years with him as my teacher, and I got a good grade at the end of it, so just keep trying and doing the work and you will make it through the year

I hope you don't get too much homework... I have got about 8-9 pieces in the last 2 days (and 7 of which are in for this week... and they include essays and pieces which take a really long time).... when I was your age, I got a lot less homework than I do now, so enjoy it while you can

If you need any help with geography or biology at all in the future, I might be able to help.. they are 2 of the subjects I chose to carry on at 6th form