Before and After
In one year, you are going to experience the biggest change in your life. It will rattle you to your core. For a while, you will view your life as how it was before and after that day. A dividing line where you had everything before, and lost it all a year later. As hard as it will be, don't view it that way. You will have the opportunity to start over in a new place. No one will know who you are, what your strengths and weaknesses are, and you can fake it til you make it on your new journey. No one will know that your mom had helped you foster all of your early friendships or planned all your get togethers.
Your brother and dad will adapt well, but I worry about you. Your brother and dad are able to move on, but you can't let go. You care so deeply of the people you formed friendships with, at the expense of creating new ones.
I want you to know that letting go doesn't mean you are forgetting. It just means you are living your life in the present, not the past. Talk with people in your classes, ask them lots of questions. (People love to talk about themselves.) :) These years will challenge and push you to your limit, but you will come out a stronger person and will see the silver lining of the struggle.
P.S. Remember to study hard for the entrance placement exams. This way you can get into more challenging classes that engage you, instead of being placed in lower, less interesting classes.
P.S.S. Don't worry about saying the wrong thing or embarrassing yourself. After high school you will move far away and will not see any of those people again (unless you decide to form great friendships with some). So have fun and don't hide who you are.