The NSW government's decision to raise the compulsory school leaving age to 17 has led to more students being disengaged at school, the state's Auditor-General has found.
The audit found many students who remained at government schools received careers advice and studied for the HSC, taking non-traditional subjects. However, some who remained at school were disruptive or did not turn up.
"Year 11 students now are absent more often and more likely to be suspended than those in previous years," Auditor-General Peter Achterstraat said. "The impact of managing these disengaged students can put a strain on other students.
"There is a risk that disengaged students not only disrupt others but also waste teachers' time.
"So more could be done to support these students."
Mr Achterstraat said schools needed to provide more programs to suit students' needs and provide high-quality career advice.
He said the NSW Department of Education needed to monitor students and better support those at risk of disengagement.
The Auditor-General found the department could not account for almost 7000 students who had not enrolled in year 11 at public schools, despite the school leaving age being raised to 17.
Mr Achterstraat's report, released on Thursday shows that of the 54,607 students enrolled at government schools in year 10 in 2010, only 47,695 enrolled at government schools in year 11 the following year, even though many would not have turned 17.
"This leaves 6912, or one in eight students, unaccounted for," Mr Achterstraat said.
"They may be on an approved alternative pathway. They may be enrolled in a non-government school. Or they may not be participating at all.
"I am concerned that the Department of Education and Communities does not know which students are not participating and therefore cannot take any action to support them."
Mr Achterstraat said that while raising the school age was an important initiative that should have a positive effect, its success lay in making sure students "don't fall through the gap".
The NSW government raised the minimum school leaving age from 15 to 17 on January 2010. If students complete year 10 but are not yet 17, they must stay at school until they turn 17, unless they get a full-time job or study at TAFE or another education and training provider.