The order - supposedly from river gods - also dictates that the students cannot make the journey on Tuesdays.
Schoolgirls in Ghana are having their education disrupted by a ban on them crossing a river to get to their school.
The students are forbidden to travel on Tuesdays because of local traditions - or when they are menstruating.
The order - supposedly from river gods - is affecting girls who cross the Offin River in Ghana's Upper Denkyira East municipality.
“There are a lot of issues impeding the development of education in the region," said Prince Evans Acquah, the area's Education Supervisor.
"But what is worrying to me is the fact that girls in the settler communities, on the orders of the gods, are not allowed to cross the river on Tuesdays. They are also forbidden to cross the river when they are in their menses."
Acquah spoke about the issue at a meeting of junior high school heads this week. It was held to discuss solutions to improve educational performances.
Many students from the Ashanti Region have to cross the river to get to school at Kyekyewere in the Central Region.
The ban on them crossing the river has shone a spotlight on the issue of menstruation affecting girls' education. Cultural taboos, together with a lack of sanitary products and suitable washroom facilities at many schools, affects millions of female students in sub-Saharan Africa.
UNICEF's menstrual hygiene ambassador Shamima Muslim Alhassan said the order in Ghana violated girls' rights to an education.
She told the BBC: "Girls say that when they are in their periods they are very shy to go to school. Even when they are in school, they often isolate themselves because they are uncomfortable and the environment is not allowing them to manage their health and hygiene properly."
Alhassan said that instead of engaging local authorities to allow the girls to cross the river, the alternative being suggested was building new schools on the Ashanti Region side.
She added: "We all know that putting up schools is not a day's job - so in the interim these girls will still be prevented from crossing over to school."
In many of Ghana's coastal communities, it is forbidden to fish or cross rivers on Tuesdays. They also believe menstruating females could upset the river gods.