Without prior communication, you can select a few students who appear perfectly groomed. Form a team and ask them to conduct a parade of students, similar to a fashion parade, and give a rating for each one based on their grooming levels.
You can randomly check their backpack or school bag to see how organized or disorganized they are in maintaining their books, notebooks, stationery kits, etc. How they present themselves now will likely be a habit in the future as well.
Even their mannerisms, way of speaking courteously, and the way they walk, talk, interact, and behave will reflect their future styles. These are a few ideas, and you can develop them further.