Why does he ignore me at parties?

So there is this guy! (As always lol)
We’ve been friends for around a year now and I’ve had a crush in him for a while.

He’s a very easygoing person, very friendly with everybody, likes to laugh and joke around.

I have no idea how he feels about me, but sometimes I can’t really help but think he likes me back. It’s just the way he is with me. He always acts like a bit of a clown trying to make people laugh, but I feel like with me he trying ten times harder. He’s ways trying to make me laught and catch my attention. He’s always teasing me and very touchy (not in a bad way) trying to be close to me and seem to really like my company. We have a lot of fun together and he’s always asking me to stay longer to keep him company or not go so soon in our environment which is a riding school. Here is where the down side of the story is. Our professional realationship status is trainer-student. Don’t worry not in a creepy weird way, he’s only a few years older than me. I’m 22 and he’s 26.

So well this week all week he was extra especial with me so I was feeling really good and kind of positive that he might actually like me back.
But yesterday we had a party with our close group of friends all from the riding school. And he ignored me completely. As if I wasn’t even there he acted like I didn’t exist. With everyone else he was just he’s normal self.
I realize it’s always the same story when we go to a party with our friends. We’ve never gone out alone only the two of us and to be honest I think he treys to avoid it. Though we do spend a lot of time alone at work and it’s never awkward.
Our friends are always teasing us telling him that I like him though I always act it cool and play along with it and try to make them believe that it isn’t true and I couldn’t care less and I think I’m convincing. Some of our friends question his heterosexuality and say he much be gay, though I think I know him better and I don’t think he is.

So what’s the deal? Help please!