Petri-Schule, Educational building in Flensburg, Germany.

Petri-Schule is an educational building in Flensburg featuring a distinctive red brick facade and L-shaped floor plan, with the northern wing containing classrooms and a hipped roof crowning the structure. The southern section, originally a gymnasium, was later converted into additional teaching spaces after a separate sports facility was constructed.

Architect Paul Ziegler designed this school, which opened in 1916 and was briefly renamed during the Nazi period. The renaming reflects how educational institutions were reshaped under political pressure during that time.

The building reflects Heimatschutz architecture, a style that shaped early twentieth-century German schools through regional materials and traditional forms. The red brick facade and crafted details show how local building traditions were kept alive in these educational spaces.

The school stands in the Nordstadt at Apenrader Straße 164, not on the city's southern edge. The main portal with the school name and construction date is set in the northern corner of the schoolyard. The building is in use by HLA – Die Flensburger Wirtschaftsschule and the Hannah-Arendt-Schule, so visitors view it from outside.

The building preserves its original architectural elements while serving modern teaching needs as part of HLA Flensburg today. This blend of historic fabric and contemporary use shows how the structure adapted without losing its built character.