The 29 girls set up an open Facebook group called the Hate Society. They were suspended for between two and 15 days in December.
The site has now been taken down by staff at the Grey Coat Hospital School, which caters for girls aged between 11 and 18, in Westminster, and most of the girls will have returned to school by tomorrow (Tuesday).
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Headteacher Rachel Allard said the suspensions were designed to send a "strong message" to other pupils.
She said, "We can confirm that a number of pupils have been given fixed term exclusions for between two and 15 days after the school became aware of their involvement in a hate campaign about a member of staff using an open Facebook group.
"While the offending material has been removed from the website, the school's decision to exclude these pupils temporarily was not taken lightly and has been designed to send a strong message to our whole school community that we do not tolerate such behaviour.
"The vast majority of parents who have been to see me about this incident are supportive of the school and understand why we have taken firm disciplinary action."
A spokesman for Westminster City Council said, "We support the school's decision to temporarily exclude these pupils. We are providing advice and support for the school during this time."