Michael Howard, the Conservative leader, will today promise an extra £200m to tackle behavioural problems in schools. A Tory government, if elected, would replace pupil referral units with "turnaround schools" and expand the number of places from 4,000 to 24,000.

"How can the majority of pupils, who want to learn and get on, do so if they are disrupted by one or two unruly yobs their teachers are powerless to discipline or expel?" Mr Howard will say in a speech.