A teacher with more than two decades of experience brought a replica firearm she made with a 3D printer to school to show students.
The woman took the ACT Education Directorate to the Fair Work Commission alleging her subsequent dismissal was unfair because it was disproportionate and harsh.
In a decision published this week, Commissioner Sarah McKinnon dismissed the application and said the woman "showed an astonishing lack of judgement for such an experienced teacher".
