I CAN help on Saturday (correcting I cannot). She HAS completed the training (contradicting a doubt). You MUST check the safety rules (strong necessity). An auxiliary that is normally weak can carry contrastive stress. Read each sentence neutrally, then with the correction; explain the changed focus without changing the words.
A supervised library role could suit a careful student who enjoys explaining things. In our fictional advertisement, the assistant organises books, welcomes visitors and works under a librarian’s supervision. It offers communication practice, but availability and lawful eligibility must be checked. I would prefer clearly stated duties and training to an exciting title with no conditions. Before applying, I would ask about the timetable, responsibilities, safeguarding and any payment arrangements. I would describe a real class activity honestly rather than claim experience I never had. A part-time role should not undermine school responsibilities or safety, and a student should not accept unsupervised duties simply to sound enthusiastic. Comparing this role with the weekday display job also shows why a suitable choice depends on the applicant’s schedule. A responsible decision begins with conditions, not only a job title.
Follow-up: What if you lack previous employment?
Response: Explain a relevant supervised school activity honestly and ask what training is provided.