Heads say the process for reporting concerns is bureaurcratic
Schools are suffering as a result of the merger of education and children's services departments within local authorities, school leaders say.
The merger, in England, was designed to help safeguard children and to improve the co-ordination of services.
A survey of members of the Association of School and College Leaders (ASCL), found a quarter thought services to schools had got worse as a result.
Ministers say it is vital one person is in overall charge of the services.
The ASCL says the "overwhelming expectations" placed on children's services departments in the past 18 months have meant that schools are losing out.
The changes came about as a result of the report by Lord Laming into the abuse and death of Victoria Climbie in 2000.
A new report by Lord laming is being published following the death of Baby P in the same borough, Haringey in London, in 2007 despite his having been seen numerous times by children's services professionals.
Children's Secretary Ed Balls asked Lord Laming to examine how much things had improved and whether his recommendations had been implemented properly.
In his address to the ASCL annual conference this weekend, its general secretary John Dunford will say: "The job of director of children's services has become the job from hell - responsible for everything that happens to children in their area, accountable to a huge range of bodies, spending a high proportion of the working week on corporate committees, and as vulnerable as school leaders to being sacked.
The risk was that some would "take their eye off the educational ball".
The group's survey involved 65 of its branch secretaries in England's 150 local authorities.
A total of 75% said services to schools were not as good as before the changes, while 22% said they were the same.
The ASCL also believes the system for reporting concerns about children is too bureaucratic.
John Dunford said: "In principle, it has to be right that all services for children should be properly coordinated.
"Better safeguarding for children will happen when there is more effective communication between local services.
"There must also be a simplification of the paperwork so that professionals can spend their time helping young people rather than filling in forms."
In the survey, 39% of those questioned thought changes to the way schools raise concerns about children's welfare had made it harder for young people to get the support they needed.
The new system - called the Common Assessment Framework (Caf) - requires schools to fill out a form assessing the child's situation to refer them to social services or other agencies.
Head teachers have told ASCL this can take up to two hours, whereas in the past many schools would have been able to raise the alarm about a pupil over the telephone.
Tess Walker, head of Belhus Chase Humanities College in Essex, said: "The Caf has generated additional work for schools and there is still a lack of capacity in external agencies to support young people once the form is completed."
The Westminster government insists the pulling together of children's services was the right way to safeguard children and provide joined-up services.
A spokesman for the Department for Children, Schools and Family said: "We recognise the need for local government to be free to tailor its services around local needs and resources but we believe there should be a single officer - the director of children's services - who has overall control of all services for children and young people, and a clear line of accountability.
"We believe this is the best model for delivering services which address the complex needs of the whole child as alternative structures could run the risk of different services not talking to each other properly. It's vital that these services are run out of the same office and work closely together.
"But it's not a case of either education or social care, and local authorities are of course free to develop specialist officer roles - including educational specialists - and we expect them to do so."