Teachers will have to turn a blind eye to off-the-shoulder T-shirts, bare-midriff tops, backless blouses and bikini tops worn under unbuttoned shirts, popular in the classroom during the current German heatwave.

The issue has sparked a nationwide debate after a secondary school in Sehnde, near Hanover, sent a girl home for wearing skimpy clothing.

“We do not want girls or boys to wear beach or disco clothing to school. We are aware of the opinion that this impairs the classroom environment,” a letter from the principal Helga Akkermann said.

But pupils, and even some parents, protested and the authorities are taking a lenient view.

German schoolchildren do not wear uniform and a number of states have clarified that dress code cannot be enforced by schools against the wishes of pupils and their parents.

“Legally, clothing is a personal matter for pupils, and for minors, their parents. A school can only enforce a dress code through its code of behaviour which must be approved by the parent-teacher association,” said Georg Wessling, spokesman for the Lower Saxony ministry of culture.

Two years ago, a 13-year-old pupil in the state of Mecklenberg-Western Pomerania was ordered to go home and change because the school administration deemed her attire “inappropriate”. The authorities later overruled the school saying the child and the parent had the ultimate say.

In the same year jack boots and Lonsdale T-shirts favoured by neo-Nazis were banned in schools under laws regarding World War II insignia. However, most schools say they do not intend to act to prevent the exposure of “too much flesh”.