"In a simpler world that might be feasible, but, rightly or wrongly, there are numerous local agencies which might have contact a child (do you ring round every GP and A&E in the area to see if they've had the child in to deal with injuries?), and social workers and the like, whatever you may think of them, have very busy workloads. Can you see why this isn't an option?"
Heaven forbid that taking care of children might involve making a few 'phonecalls. A simpler system would one which centralises the information only of children who have had contact with the police or GPs or A&E or social workers etc - rather than *every* child in the country. Smaller database, faster searches, more efficient use of technology. It limits information held to only those children who are actually at risk or already in bad situations; it limits access to the people in the local area who might have a legitimate reason to access the information; it curtails the tendency towards mission creep inherent in all of these government IT projects.
The money saved could be used for better training, more social workers, implementation of better information sharing protocols. Basically, spent on anything other than a needless (and needlessly expensive) address book of kids.