Would 'separating disruptive students from the rest ruin their chance/chances'? (The sentence could perhaps continue like, '...chances of gaining social skills. But can we just stop there? And if yes, then could it be 'chance', without 's', as well?)
Note that your title should have read "To ruin someone's chance/chances"
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.