When the girl, who was aged 13 at the time, questioned Herewini about what he was doing he told her to shut up before he removed her underwear and sexually assaulted her.
Before leaving, Herewini threatened to hurt the girl if she told anyone what happened.
About a month after the sexual assault the girl reported it to the school nurse.
The jury began its deliberations on Wednesday afternoon after all of the evidence had been heard but had not reached a decision by the end of the day so they resumed again on Thursday morning.
Herewini was found guilty on all three charges.
Judge Edwards remanded Herewini, who was aged 23 at the time of the attack, in custody to reappear for sentencing on November 18.
Where to get help:
If it's an emergency and you feel that you or someone else is at risk, call 111.
If you've ever experienced sexual assault or abuse and need to talk to someone, contact Safe to Talk confidentially, any time 24/7:
• Call 0800 044 334
• Text 4334
• Email support@safetotalk.nz
• For more info or to web chat visit safetotalk.nz
Alternatively contact your local police station - click here for a list.
If you have been sexually assaulted, remember it's not your fault.
