Final answer:
The 'rule of thumb' for appropriateness of a particular hairstyle when in uniform is that it must not obstruct vision. Hairstyles should be neatly tied back or secured to keep hair away from the face and eyes. This is important for safety reasons, especially in certain environments like laboratories or kitchens.
Step-by-step explanation:
The 'rule of thumb' for appropriateness of a particular hairstyle when in uniform is that it must not obstruct vision. This means that hairstyles should be neatly tied back or secured in a way that keeps hair away from the face and eyes. This is important for safety reasons, especially in certain environments like laboratories, where hair can pose a hazard.
For example, in a science lab, long hair should be pulled back to keep it away from bacterial cultures and open flames. Similarly, when working in a kitchen or handling food, it is important to keep hair secured to prevent it from falling into the food or creating a hygiene issue.
By following these guidelines, students can maintain a professional and safe appearance while in uniform.