Following the first investigation, families were told by the Crown Prosecution Service (CPS) that the driver would not be charged as she had suffered an epileptic seizure.
Ms Freemantle publicly expressed her “deepest sorrow” and said she had “no recollection of what took place”.
The girls’ families said they remained “unconvinced” that the investigation had been conducted thoroughly.
The Study Preparatory School’s current headteacher Sharon Maher and former headteacher Helen Lowe, who was in charge at the time of the crash, have also said they felt let down by the first Met Police investigation.
They previously said they were “angry, sad and confused” by the decision not to prosecute.
Four months later, senior Met officers have now decided – following an internal review – to open a new investigation into the crash.
The force said: “The review has identified a number of lines of enquiry that require further examination and, as such, the investigation will now be reopened.
“The families have been updated with this development and we will continue to meet with them to provide updates on the investigation as it progresses.
“We know this has been and remains a really difficult time for them.
“We believe this further investigative work will address all questions raised by the families affected.
“This further investigation will be undertaken by an accredited senior investigating officer and team with experience in homicide investigations.”
The families of the children who died have welcomed the new investigation.
