Heads who are made "critical friends" for other schools will be expected to spend around 40 days a year helping them.
The Department for Education and Skills this week revealed new details of its plans to provide every headteacher with a school improvement partner (SIP).
Secondary schools will usually be assigned a serving or former headteacher as their partner while primary schools are likely to be sent an officer from the local education authority.
All SIPs will undergo "brisk" training and will be able to gain accreditation for their work. Their jobs will include identifying their assigned school's needs, supporting it and acting as a go-between between the school and local and national government.
Their relationship will be more formal than that with primary consultants.
John Dunford, general secretary of the Secondary Heads Association, said headteachers would not be overworked by acting as SIPs for 40 days a year, because they already spent a large proportion of their time working with other schools.
David Hart, general secretary of the National Association of Head Teachers, said: "There is only a relatively small number of heads of the right quality for this challenging job. And if they try to foist local authority staff who do not have recent school experience on to primary schools they will be doomed to failure because they won't have the street cred."
SIPs are at the heart of the Government's "single conversation" plan, which aims to give every school a single person they can talk to about their needs.
Newcastle's 11 secondary schools have been working with their own school improvement partners for the last two years. The city's education authority wanted its school advisers to have had the experience of working as heads.
But while it could afford the salaries of former primary heads, experienced heads from the secondary sector were out of the advisory service's price range.
Instead, three serving or recently retired heads from other areas of the north of England have been employed as consultants to work with the city's secondaries.
David Pearmain, head of Kenton school has just had a visit from his partner to look over his school improvement plan. "Because they are not next door to us it gives them a different perspective and because they are heads they are aware of the practical problems of running a school," he said.
He also values that fact that his school improvement partner is not a direct employee of the LEA and is there to support and challenge the school rather than enforce the authority's policies.
"If they act like Government inspectors then I don't think this will be positive," he said.