Tighter controls on the use of biometric identification data in schools are being considered in Gloucs.
Biometric systems are used in school for registration and payment
An investigation by the county council found 29 schools, with a total of 8,400 pupils, used such systems, and another seven were considering the option.
Restrictions will be brought in to protect parents' rights as well as the privacy of children, the council said.
The systems use fingerprints, retina and iris patterns, as well as voice waves, to recognise an individual.
Councillor Jackie Hall, cabinet member for services to children, said: "If biometrics are to be used in Gloucestershire schools I want to be sure there are firm and fair guidelines laid down.
"These systems are legal and supported by government policy.
"However, we recognise that they are not essential and that the use of biometric data is associated with additional risks and security issues.
"It is ultimately a decision for individual schools and governors but the county council strongly recommends that schools should consider all the implications.
"If schools do wish to use biometric data of children and young people then they should have the written permission of parents beforehand and effective safeguards must be put in place to ensure security of any data collected."