Altstädter Schule, School building in Celle, Germany.

Altstädter Schule is a three-storey flat-roofed school in Celle, built 1927–28 to Otto Haesler's design. Two taller side wings with classrooms flank a lower central hall, 25 by 14 metres, originally lit by a Luxfer glass-prism skylight. Over 3,000 panes in horizontal window bands give it the nickname Glasschule; painter Karl Völker coloured the interiors grey, blue and red.

Built in 1928 by architect Otto Haesler, the school attracted significant public attention at its opening. It quickly became a noted example of modern school architecture in Germany and beyond.

The building is nicknamed "Glasschule" because of its window bands with over 3000 panes. Painter Karl Völker chose the original colours: light grey walls, blue curtains and red doors in the classrooms, with a red canopy marking the main entrance.

The building is located at Sägemühlenstraße 9 in Celle and is easily visible from the street. The architecture can be fully viewed from outside, and the site is straightforward to reach.

The central hall, 25 metres long and 14 metres wide, was originally lit by a skylight of Luxfer glass prisms. In the 1980s wood panelling and a suspended ceiling covered this daylight feature, altering the room's original spatial effect.