Girls going into their first year at a Jersey school will not be able to wear skirts after a ban.
Haute Vallee head teacher, Caryl Lewis, says the change will smarten pupils' clothing and stop inappropriate dress.
She said it was being introduced after concerns some skirts were too short and others were being rolled up to make them shorter.
Ms Lewis said the change would be phased in over the next three years and did not apply to girls already there.
She said: "Sometimes you have so many variations and skirts can become too short and that is inappropriate in the work place and our school is a work place."
Heidi Stephenson, assistant head teacher at girls only Catholic school, Bealieu, said it would not be something her school would be following but understood why Haute Vallee were doing it.
"I actually think it sounds very sensible and can understand why schools are doing this, it is important students turn up at school dressed appropriately for learning," she said.
"I don't necessarily think Bealieu will need to follow at the moment but we constantly look at our uniform policy to check that the girls are wearing it appropriately," she said.
The school aims to be skirt-free by 2015.