The Conservative leader, Michael Howard, is calling for better school discipline.
Parents' advisers say special educational needs are often the issue
As part of a wider-ranging speech on crime, Mr Howard has again committed the Tories to abolishing independent exclusion appeal panels in England.
He wants head teachers and governors to have the final word on discipline within their schools.
But parents' advocates say this would probably result in many more exclusion cases ending up in court.
The Labour government has changed the rules and guidance covering the independent panels.
Their make-up was changed so that most of their members have school-based experience.
They are duty-bound to balance the interests of the excluded pupil against the interests of the whole school community.
And they are told it would be "inappropriate" for them to reinstate a pupil who had been permanently excluded for serious actual or threatened violence, sexual abuse, selling illegal drugs or persistent and malicious disruptive behaviour.
It is highly unusual for pupils who have been excluded to be reinstated on appeal.
The most recent annual statistics on permanent exclusions in England, for 2002-03, show that of the 9,290 exclusions there were 1,074 appeals, of which 21.1% were successful (2.4% of all the exclusions).
Of those successful appeals, reinstatement of the pupil to the same institution was ordered in 71.3% of the cases - about 160 pupils or 1.7% of the total exclusions.
But the Conservatives - who have published a dossier of case studies - say violent and disruptive pupils "are causing misery for teachers".
There were more than 4,000 estimated exclusions for attacks by pupils on adults in the summer term of 2003.
Last month, the mother of murdered schoolboy Luke Walmsley said it should be easier for schools to expel those like the "evil bully" who killed her son.
In his speech on Tuesday, Mr Howard said discipline in school was essential if children were to learn respect for authority at an early age.
"I suspect that I am just one of millions of parents and grandparents bewildered and horrified by the breakdown in discipline in our schools," he said.
All too often it was teachers - not pupils - who found themselves on the wrong side of the law.
"Only recently we had the nonsense of a teacher taken to the crown court to stand trial by jury because she had - in jest - put some tape over the mouth of a child."
Disruptive and violent pupils ruined the education of every other child in the class.
"We will introduce enforceable home-school contracts that spell out both parents' and pupils' responsibilities," he said.
"And we will give heads complete control over expulsion. If they decide to expel a disruptive pupil, they will not be second-guessed by an outside panel."
Margaret McGowan of the Advisory Centre for Education, which helps parents, said it would be alarmed if appeal panels were abolished.
"Without the independent appeal we think there would be an awful lot more cases going to court, which would be unfortunate."
It was a "myth" that most exclusions were about "young thugs carrying weapons".
Often what lay behind a case was a failure by the school to provide for a child's special educational needs.
She said the appeal panels were "skewed", with a preponderance of school representatives and only one lay member.
Rather than being abolished they should be improved.
The centre would prefer to see them run along the lines of tribunals, made up of experts and with a legally qualified chairperson.