I've not had any dealings with Child services, but I'm assuming you would have dealings with them before they take the children either by phone or visits etc....the best time for the petition would be their first contact with you...create the petition and give to the proper court representative?
Printed copy · Anthology Volume 9, page 155Printed copy from The Tender For Law Anthology, Volume 9, page 155 (printed 13 June 2014). Added by this site; not part of the Facebook export.