China has a huge population, but with less diversity than many North American or European countries—so foreigners do stand out. This is particularly true of smaller cities where Western visitors are rarer. In certain places, you might be some of the first foreign or Western people your students have ever met, or at least got to know. Similarly, many older Chinese people won’t have travelled much or at all, and so will be even more likely to be surprised when they see you.
A natural consequence of this is that foreigners can get treated with great hospitality and locals tend to be very friendly, generous and curious about you. The same impulse means it is common for visitors to be stared at or have their photos taken without permission. People may take photos of you, sometimes subtly and sometimes not. You might get asked to pose for photos, particularly with children, or people might simply take a photo of you while you’re not looking. This will probably become quite normal to you after a while, but can be a bit strange the first few times—remember that nothing negative is normally meant by it, you’re just more noticeable and unfamiliar. Whilst it may cause awkwardness in some cultures to realise that someone has noticed you staring at them, in China this often isn’t the case; again, nothing is meant by it.