How should I get his attention?

hi. okay so in my pe period there's a bunch of other classes, and the ta (teachers assistant- also a student in case you don't know) is pretty cute. haha so sometimes I see him around school and when I walk by I think him/the guys he's with get louder, or sometimes he looks at me, but he usually wears sunglasses so it's hard to tell. he drives home with a bunch of his friends, and one time when him and his friends were driving past me and my friend they whistled, like a cat call or whatever you call that. haha. and we were like the only girls they would do that to around so I'm sure it was to is. the first time, one of them spit out the window about 10 feet in front of us, not to spit on us or anything, but to land around us. idk why they did that haha. but I'm just wondering what you guys think I should do to maybe start talking to him or something. thanks :*

and it wasn't him that spit, it was a friend in the same car. and he didn't try to spit on us, just near us... if you have any idea why he did that it would be appreciated lol