Pressure to broaden the use of identification numbers attached to preschoolers has concerned the Privacy Commissioner.
Most children in early childhood education (ECE) have been assigned a national student number under a new Government project.
The Ministry of Education says the numbers are necessary as they give it an accurate picture of enrolment, attendance and teaching at ECE centres.
It has had limited information on early childhood education participation and its impact on later achievement, and individual information on children will allow much better development of policy and allocation of resources.
However, considerations about how else children's information might be used have created angst in the ECE sector, and Privacy Commissioner John Edwards has kept a close watch.
Notes prepared for Mr Edwards before a meeting with the ministry's chief privacy and information security officer in October spell out those concerns.
"Extension of the NSN [national student number] to the early childhood sector was justified," states the "talking points" note, released under the Official Information Act.
"But we remain concerned at the ongoing pressure to broaden the scope of NSN use and to use education data for other purposes (e.g. social services)."
One consideration has been to use children's data to police beneficiaries.
New obligations require beneficiaries to take reasonable steps for their children to attend early childhood education from the age of 3, or have their benefits cut.
The prospect of attendance information being passed on worries ECE providers, who are vehemently opposed to "dobbing in" parents.
The Ministry of Social Development has previously said that such an exchange could be considered "over time".
Documents show that in October, the Office of the Privacy Commissioner urged Ministry of Education officials to detail how the use of children's information would be restricted, "particularly in relation to the use of NSNs to encourage and facilitate ECE attendance".
Asked if such an exchange has been ruled out, Lisa Rodgers, the ministry's head of evidence, data and knowledge, said it was not "an active area of policy".
"There are no plans for information sharing with the MSD to use [children's] information to ensure beneficiaries' social obligations."
Ms Rodgers said the ministry was recently approached by the Midlands Health Network, who want access to NSN information.
The network is running a child health service on behalf of a number of district health boards, and believes ECE information could be used to find families it had lost track of.
"We are taking a cautious approach to this proposal. We are taking a range of advice on what steps would need to be taken to meet privacy concerns," Ms Rodgers said.
Peter Reynolds, chief executive of the Early Childhood Council, said the ministry's Early Learning Information (ELI) system was a "new toy".
"There is a general amount of enthusiasm across the ministry about what information possibilities there are to derive from ELI data, but they are still exploring that themselves.
"We are concerned about the general excitedness of having a new toy."
Assistant Privacy Commissioner Katrine Evans said any transfer of "unique identifiers" like the numbers assigned to preschoolers between Government departments or sectors had to be very carefully considered.
"There is a possibility it could become a way to link records in a way that people wouldn't expect."
What is information sharing?
Information-matching or sharing is the disclosure of personal information about an individual by one government agency to another.
In tough economic times such sharing can save the government tens of millions of dollars, but its expansion comes at a low ebb in public confidence in information-handling, after several high-profile breaches.