It had previously been announced driver Claire Freemantle wouldn’t face criminal charges over the incident last July.
Scotland Yard says it’s now found a ‘number of lines of enquiry that require further examination’.
Nuria Sajjad and Selena Lau died last July when a 4-by-4 careered into the grounds during an end-of-term picnic at the school on Wimbledon Common.
Families were unconvinced by original inquiries which found the driver had a seizure.