I'm in band and I can play a 1 clarinet part but I usually play 2 clarinet but I'm almost 1 I don't think my band teacher thinks that I can actually play 1 clarinet but I have before what should I do

You should talk to your band teacher about it. Or if you want to be less direct you can record a few sound tapes and ask your teacher if your good. Also try asking for a copy of 1st part "Just for fun." Im a t sax player at a small school with only 4 symphonic tenors. My band teacher gave me 3rd chair. I almost always get 2nd because 1st chair is a grade older than me. But the last concert of the year he gave me 3rd. I started dropping hints like "Accidentally" sitting in the wrong chair or "Accidentally" leaving stuff on the 2nd chair. Turns out it was cuz the girl that got 2nd chair had to get out easily to switch to bari sax. But I got that info. GOOD LUCK!