I study in a girls' school in Scotland. There are no boys in the school, however there are some male teachers. I share a room in the school with my friends. Is it Haram to take off my scarf in front of these girls only?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

The Awrah (parts of the body that must be covered) of a Muslim woman in front of a Muslim woman is from navel to knee. Therefore, if you are assured that alien men or non-Muslim women cannot see you then there is no harm to remove your headscarf; otherwise, it is forbidden. For more details, please read the Fatwa: 81343.
Allah knows best.