I was that way in 9th grade, minus the binging. You have to look at yourself and just look at what is the truth. I was 250 when I was walking around at school with no friends and people harrassing me everyday. I wore the same clothes everyday and missed school a lot. I missed 2 weeks just from depression from all of it, which made things ten times worse.
You have to go to class and do what you have to do no matter how you feel. Only after can you start working on yourself. When you miss classes you get stressed which doesn't cure binging at all.
You have to realize you're 143 and probably not far from your goal. 20 pounds away from goal? 30? That isn't so much if you work bit by bit at it.
If you keep binging you'll be 160 before you know it...then 200...then 250...You know? All I can tell you is to go to class, get your outside world life on straight, then work on yourself.
If you worry about calories or trying to do a specific diet, just stop. Eat 3 meals a day (regular meals) for awhile and try to find some control. I know it's hard, but worrying and obsessing makes it 10x harder
I'm hard on you because I was in the same situation so I know how it feels. I want you to get better.