Rory's mother dropped him off near Meldrum Primary School in Livingston, West Lothian, last Thursday morning.

He did not attend school - but was not reported missing until that afternoon. His body was discovered on Sunday.

Around Britain the policy on reporting children missing from class is decided largely on a school-by-school basis.

On an average day, 50,000 pupils in Scotland - 7% of the school population - are off because of truancy, illness or holidays.

A Scottish Executive spokeswoman said head teachers were "better qualified" than officials to deal with individual cases of absence.

Thousands of pupils are missing from school each day

She added: "The school will know the individual pupils and their behaviour and what is normal for them.

"It's too early to speculate what's happened in this [the Rory Blackhall] case.

"We will look at this with head teachers and parent bodies to see if there are any particular steps we can take to tighten up the child protection part of absence reporting."

Various pilot projects have been started in Scotland since five-year-old Danielle Reid from Inverness was murdered by her mother's partner in 2002.

Her mother had withdrawn her from school and lied to teachers, saying the family was relocating to Manchester.

Further tracking of children's movement between local authorities has since been introduced.

Some schools have installed phone systems which make it easier for parents to report absence for reasons like illness, thus helping the school to monitor pupils' whereabouts.

Another scheme is being piloted this year, where parents are automatically contacted by mobile phone text messages if their child fails to attend class.

A Convention of Scottish Local Authorities spokeswoman said: "The public should be assured that councils work with their schools to ensure that reporting procedures meet the needs of local communities.

"We welcome the executive's recognition that there is a need to combine local knowledge and local judgement in making the most appropriate responses to individual situations."

As in Scotland, schools in England themselves decide policy on dealing with unauthorised absences.

Head teachers decide what resources they allocate to the problem.

Computers allow schools to monitor children's absence

In June, a report by the National Audit Office found most had "a clear policy but there can be problems with communicating the policy to staff and parents, leading to inconsistent implementation".

Most secondary, and some primary, schools used electronic registration, but a small minority "had difficulties using it effectively".

In many cases, where a child's absence has not been explained, there is a system of "first-day calling".

The electronic register, noting a missing pupil, tells administrative staff, who telephone the family.

The NAO has recommended that the Department for Education and Skills expand this programme. A DfES spokeswoman said schools were encouraged to do so.

The Welsh Assembly Government has issued guidance to all schools.

This urges parents to inform staff as soon as possible if their child will not be attending on a particular day.

If a pupil is absent without explanation, the school should, wherever possible, contact the parents the same day.

Some �6m is being provided over the next three years for electronic registration packages.

A spokesman said: "These are proven to improve attendance in schools as they provide information on individual pupils' attendance at an earlier stage than manual registers.

"This allows schools to react more quickly and chase up non-attendees."

As in England, these will be linked to "first-day contact" systems.