Julie Kaputa, an honors student at Beaver River Central School in Lewis County, was suspended after she brought coffee to class and refused to throw it away.
Kaputa was violating a new district rule banning outside food and drinks at school.
But Kaputa and her mother questioned whether the policy had been properly adopted.
The district's code of conduct requires a public hearing before changes are approved. Kaputa said she could not find notice that a hearing on the new policy had been scheduled.
The district's superintendent later acknowledged that a hearing held in August was not properly advertised and praised Kaputa for speaking up about the issue.
Kaputa's suspension will not appear on her permanent record.
The district said the outside food and drink policy is intended to create a safer, distraction-free learning environment.
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