New advice issued by the Scottish Government means that anyone working or meeting regularly in a school - even when no children are on the premises - is legally obliged to have a disclosure check.
The U-turn follows a re-examination of recent child protection legislation by officials. They have now reversed their previous advice, which stated that police checks were only required when someone was appointed to a post or position where normal duties included childcare.
The new advice, however, means that participants in, for example, an adult learning class or parent council cannot meet on school premises unless everyone has undergone checks by the Central Registered Body in Scotland to ensure they are not on the list of people deemed unsuitable to work with children.
It means that workmen building a new school, which has yet to be opened to pupils, would be covered by the act's provisions.
Judith Gillespie, development manager of the Scottish Parent Teacher Council, who has led a long-term campaign to make the disclosure system less restrictive, warned that there would be a huge impact on parental involvement, particularly in certain areas: "You can forget about community use of schools."
The decision to re-examine the Protection of Children (Scotland) Act 2003 was prompted by a meeting between the SPTC and the Children and Early Years Minister, Adam Ingram, last September.
Mrs Gillespie said Mr Ingram seemed sympathetic to their arguments for a lighter, more proportionate approach to checks.
However, when officials re-examined the legislation, commonly referred to as Pocsa, they came up with a fresh interpretation.
Schedule 2 of Pocsa defines anyone in a "child care position" as a person whose normal duties include work in an "educational establishment" (other than a university), which, in turn, is defined as both the institution and the premises. The act defines work in this context as "work of any kind, paid or unpaid, under a contract of service or apprenticeship, under a contract for services, or otherwise than under a contract".
Simply put, participation in everything from a further education course to a regular social activity is deemed to be a "child care" position by virtue of its taking place inside a school or college.
A Scottish Government spokeswoman said the act did not apply to "ad hoc" situations, such as a school disco, but to regular meetings or employment. "We are aware of concerns around the position of parent council members and are investigating this before taking whatever action is necessary," she added.