How Do I Ask A Guy Out In High School (gay)

I (15M) am wanting to ask out this guy I have liked since the start of the school year. It is just over 1 week until the end of the school year. I'm out to everyone in my school, so he knows I am gay. 

I didn't even know who this guy was until September when I first shared a lesson with him and I would say we are mates now. I have no clue if he likes boys, but he hasn't a girlfriend since I have known him while almost all of his mates have (I don't know if that suggests he is gay or anything).  

I want to ask him out before summer since if he says yes, I won't have 6 weeks without seeing him and if he says no, there will not be 6 weeks of awkwardnees building up (I feel like it woukd be less awkard if I see him the next day). He has shown interest, however I have no clue if he is just being friendly. We make eye contact quite often and I did feel a bit of tension between us up until the first time we actually spoke (back and forth, not just a humorous comment). 

His mates randomly started being very active with me in school and constantly saying things about him since this one date (by date I should clarify, I mean like on a calendar and not a romantic date or anything). On that date, I remember his mate coming up to me and saying how he has been chatting shit (in a banter way) and I should have him. He led me to where he was and we had a bit of a moment where I was a bit physically close to him (I was eating at the time so I didn't say a word). Ever since then, they have enjoyed talking to me, which leads ne to believe he told them he likes me or something (obviously, I might just be delusional). I have his snapchat, aswell as TikTok, Instagram and even fricking Lemkn8 (I am his only follower and he is the only person I am following). The same day I came out, he added my snapchat (take that as you will).  

I have thought about telling one of my mates that I like him and ask for their advice as they will definitely be more useful than Redditors who don't even know who he is. The only thing stopping me from telling a mate is that all of the options I have will take the piss out of me heavily if he doesn't even like boys. It is the same reason why I haven't asked him out yet.  

I don't fancy asking him on a date or anything, preferably just ask him to be my boyfriend. It is his birthday soon, do you think wishing him a happy birthday over Snapchat is a good idea (I don't wish any of his mates a happy birthday). If yes, I wouldn't do a story, I would do it privately like I do with my mates (I have never understood the idea of not just messaging them directly). 

I am willing to answer almost any questions you have (to an extent). Thank you in advance