In most female-only schools, there are always male teachers around. Hence wearing even body suits is not sufficient, therefore to remove yourself from this activity is the only solution. There are some female-only baths or swimming complexes, yet even this is not suitable for the purposes of Muslim women. The following tradition treats this point:
"Some women from Homs or from Sham (now the area of Damascus) came to 'A'ishah. She asked, 'Do you enter the public baths? I heard the Messenger of Allah saying that a woman who undresses anywhere else other than in her own house tears off the Satr (shelter) which lies between her and her Lord .' " [At-Tirmidhi and Abu Dawud]
It is not only a problem of Satr, but also revealing yourself to disbelievers, an important point which ssisters are ignoranor careless of. Permission for a Muslim woman to reveal her hair, arms etc. is permitted to her husband, father, mother and so on.
Non-Muslim women are excluded from this permission, because contact with them might easily lead to disastrous results. That is why the Khalif 'Umar wrote to Abu 'Ubaidah Ibn al-Jarrah, the Governor of Syria, to prohibit the Muslim women from going to the baths with the women of the Ahl al-Kitab (the People of the Book). [At-Tabari, Ibn Jazir]. According to Ibn 'Abbas "...a Muslim woman is not allowed to display herself before the women of the unbelievers and non-Muslim poll-tax payers (Ahl al-Dhimmah) any more than she can display herself before other men" [At-Tabari].