AN INCREASING number of students are disrupting classmates and wasting teachers' time since the state government raised the compulsory school leaving age to 17, says the NSW Auditor-General.

While many schools are providing careers advice and options such as vocational subjects for the HSC, many students remained disengaged.

Disengaged ... an increasing number of students are disrupting classmates and wasting teachers' time.

Auditor-General Peter Achterstraat said some students at school in year 11, who may have otherwise left, were disruptive or truanting.

The department of education could not account for almost 7000 students who did not enrol in year 11 at public schools last year, despite the leaving age being raised to 17.