Police believe the man who sexually and indecently assaulted two young girls in a Guildford toilet block had previously attacked primary school pupils in Haberfield in Sydney's inner west.
Child Abuse Squad detectives this week released two facial identification images of a man wanted for questioning over both child sex attacks.
The two sisters, aged two and six, were followed into the public toilets at Campbell Hill Pioneer Reserve and sexually and indecently assaulted on January 9.
Both girls were found crying from the "harrowing experience" police said.
The man was described as tanned, medium to thin build and wearing a blue and white checked shirt, jeans, dark sunglasses and a baseball type hat.
Detectives say they have now established "direct links" between that attack and the assault of four young girls at Haberfield Public School on May 17.
The students were sitting in a stairwell at the school about 10.20am having their recess when they were approached by a man who sexually assaulted one girl and indecently assaulted two others. Another girl was struck in the face before the attacker ran away.
He was described as being tanned, with a medium to thin build and was wearing a blue and white checked shirt, jeans, dark sunglasses and a baseball hat.
Separate police strike forces were formed to investigate each incident but now the Child Abuse Squad has taken over the cases.
Police have have urged parents to discuss safety messages with their children including reminding them not to talk to people they don't know, to yell out if someone tries to touch to them and to walk near busier roads and streets.
Anyone who recognises the man, or who has information about the attacks, has been urged to contact Crime Stoppers on 1800 333 000 or visit the Crime Stoppers online reporting page through www.police.nsw.gov.au.