Most Helpful Guy
Something that probably should have been discussed at break up. I wouldn't say anything personally unless he does to you. Be cordial.
Most Helpful Girl
You both are no longer this item so the writing is in on My wall and all here, dear, that you might as well get used to Seeing him daily Being... He's in the same class.
Be civil if he speaks to you. No use putting your head down when he is around. This will show Him this split is making you a cold stone and with You Not being Friendly... Don't let him get the Best of you.
However, if he wants to be 'Like this' with putting you on his pay no mind list, just ignore him and The... Class will carry on till all are dismissed.
Good luck. xx