@Spirit002,
It's not just societal opinions; it's likely the law. It's also your future career.
Don't ask him for his number. Get some therapy instead. Find out why you're fishing in the wrong pond, and why you aren't allowing yourself to find someone more your own age. Find out why this forbidden fruit is so enticing for you that you're willing to lay waste to your future for it.
Your 17 year old pal could easily blab to just about anyone, and not necessarily intentionally. Being found out doesn't just embarrass you. It also, potentially, torpedoes not just whatever job you're going to but also, maybe, future jobs.
No one is going to want to hire a teacher who looks for love amongst his/her underage students.
And this is assuming you don't get into a situation where you could be tagged as a sex offender. For life.
Think I'm being an alarmist? There are a lot of out of work people right now. If you crash and burn your job, they will be only too happy to take it. And parents aren't going to listen to protestations that he's almost 18 and you're in love or whatever.
They are going to look at you and think
Pamela Smart.
This is foolishness, and I hope you can see past the here and now and realize that.