Handclaps are being used instead of school bells
Islamist militants al-Shabab have banned teachers using bells to signal the end of class in the town of Jowhar, 90km (56 miles) north of Mogadishu.
Al-Shabab said the bells sounded too much like Christian church bells.
This comes after last week's order by the Hizbul-Islam group that radios stop playing music because it is un-Islamic.
A teacher told the BBC's correspondent in Somalia that handclaps were now being used instead of bells to bring classes to an end.
The end of classes is also marked by teachers beating on tables and doors, reports the Associated Press news agency.
In the past, Islamist militants have banned watching films and football, as well as musical mobile phone ring-tones, says the BBC's Mohammed Olad Hassan in Mogadishu.
They have also carried out amputations and lashings for theft and stonings for adultery.
Last week, al-Shabab closed down BBC radio relay stations in five cities in southern Somalia, including Mogadishu.
Somalia has not had a functioning central government since 1991 and the Islamist militants control large parts of its territory.
The transitional government - backed by African Union troops and UN funds - controls only a small part of the capital, Mogadishu.