The school denied it dismissed Ms Zhou, claiming she resigned immediately after being confronted with Ms Shi's concerns.
But the Employment Relations Authority has found Ms Zhou was dismissed, noting she was apparently under pressure to leave immediately.
Authority member Rachel Larmer said Ms Zhou left part-way through the day, did not say goodbye to colleagues, did not collect all of her personal belongings and sat in the car park crying after she was sacked.
The authority also found Ms Zhou was given minimal information about the allegations against her, and her dismissal was unjustified.
Ms Larmer ordered St George to pay $4050 in lost wages, $3512.94 in unpaid holiday pay, commission and wages, and $3571.56 in legal and filing costs.
She also ordered the school to pay $5000 in compensation for the "high degree" of humiliation, distress and anxiety which Ms Zhou suffered.
The dismissal left her embarrassed about having to turn to her parents for financial help, and anxious about her immigration status because her visa was linked to her employment at St George.
"Ms Zhou was tearful during the authority's investigation and it is evident these matters still weigh heavily on her," Ms Larmer said.
However, the authority reduced the compensation by $750 to reflect Ms Zhou's contribution to her dismissal.
Ms Zhou was not at fault for sending documents from her own email address, given the school's "notoriously unreliable" email system.
There was also insufficient and non-specific evidence about her passing on a student's personal information.
However, Ms Zhou was to blame for failing to tell the school that its former principal had taken copies of employment agreements when he left - a fact the former principal had asked her to cover up.
The authority reduced the total compensation amount to $4250.