Candidates can apply after 12th or after graduation as well because there is no such particular requirement to apply as the only need is good communication skills . Also there are many BPOs available which provide recruitment on the basis of 10th, 12th, Graduation etc. Also, BPOs jobs can be opted as part time work as well as students do the same during their college time for the sake of pocket money as it is common now a days.

Good Luck!!!