Truancy charges against the parents of the Kuranui College student were dropped in the Masterton District Court on March 5.
That followed the school saying it had become aware of medical issues affecting the girl that it had not known about.
Kuranui College was a school which placed a great deal of emphasis on the attendance of its students, Mr Shepherd said.
"The other important thing is 'Why do we bother?' [We care] because kids have got to be in school, because if they're not in school they're not learning," he said.
"If their attendance drops below 80 per cent, then they're not learning effectively and we take it very seriously."
"If they miss classes, the progression, the continuity, starts to become impaired.
"It's a major worry for us."
He said when such students returned to class, they were inevitably behind.
"Then they are in catch-up mode."
The effects were serious if students were cutting junior school classes, Mr Shepherd said.
"It becomes very obvious when it comes to NCEA.
"It really starts to bite them for levels 1, 2 and 3.
"This is why we put a lot of emphasis on it."
Kuranui appealed to parents to help by getting their children to school.
"If you have a pattern of non-attendance, you have a fall-off in achievement."
Poor attendance at primary school was also a concern, because it got even more difficult to rectify that at college, he said.
The weeks and months leading up to the case had been a difficult time for the school which received several derogatory emails in the aftermath of the case, Mr Shepherd said.
"We found it quite tricky, the whole process, because it becomes very public."
The father, who has name suppression to protect the daughter's identity, said they had done everything in their power to ensure she attended school.
The man said Kuranui College had not written or communicated with them about his daughter's truancy.
They were only made aware of the situation when they received a summons to attend court, he said.
Kuranui College denies that accusation.
The girl is still not attending school, but at the age of 16, is no longer legally required to do so.