The police were called to the school and officers spoke to three girls.
The girl, who cannot be named due to her age, has now been charged with a common assault against Charlene Ponteen, vice-principal of Haberdashers’ Academies Trust South.
The girl is also charged with possessing a sharply pointed article at the school on May 15, the day before the lockdown incident.
She is said to have had a hairbrush which was sharply pointed on one end.
The girl is set to appear at Bromley Magistrates’ Court this week.
Parents from Haberdashers’ Knights Academy received the following letter from the school: “Dear Parents and Guardians,
“You may be aware that we have had an incident of three pupils from another school entering the site today.
“They did not enter the school building. I want to take this opportunity to provide further clarity and reassurance about what happened and how we responded.
“The individuals involved were pupils from another local school who came onto our school grounds without permission.
“Our staff acted swiftly and in line with our safeguarding procedures to ensure no-one was placed in danger.
“The police attended promptly and as a precaution, we implemented our lockdown procedure.
“The safety and wellbeing of our pupils and staff is our priority and I want to reassure you that they were safe at all times and no one was harmed and we will continue to support them as needed.
“We have been in contact with the leadership team at the other school and they are committed to working with us, and their students to avoid this happening again.
“We understand that incidents of this nature can be unsettling and we are committed to keeping you informed.
“We are also mindful of the importance of protecting the wellbeing of everyone involved, including our own pupils and staff, by avoiding unnecessary speculation or the sharing of incomplete information.
“We kindly ask for your support in allowing us to manage this matter appropriately, and to come to us directly with any concerns or questions.
“If you do have any questions or would like to speak to a member of the school team, please do not hesitate to get in touch by contacting the school reception.
“Thank you, as always, for your support and partnership.”
