Some young persons are entitled to time off work for study if they have not achieved prescribed standards of achievement, but what are these prescribed standards?

Some young persons are legally entitled to a reasonable amount of time off work for study if they have left full-time education without achieving, for example, grades A to C in five GCSE subjects; or SQA standard grades at grades 1 to 3 in three subjects; or one Intermediate level GNVQ.