The National Audit Office said teachers might not be the top priority for vetting procedures.
In a study of the Criminal Records Bureau, the watchdog said there had been increased public concern about the safety of pupils following the Soham murders by school caretaker Ian Huntley.
The largest number of applications for criminal checks were for adults working in education.
The NAO said: "Experts have suggested that children in schools may not be the most vulnerable to abuse."
The report added that over-65s were more likely to be abused than children, and that sex offenders were particularly likely to get jobs caring for people with learning difficulties. Young people were more likely to be abused by sports coaches than teachers.
Education has long had comprehensive and proven protection processes, while sport has only just come on board.
The watchdog concluded that Home Office research was needed to see if the CRB was reducing the numbers of abuse cases.
Criminal Records Bureau: Delivering Safer Recruitment is at www.nao.gov.uk