why do my students hide?

It is not the first time i met students outside of school.

Once I met a particularly naughty little girl from a P3 class at IMM. She stopped dead in her tracks and amazingly took her noly 1 split second to find her escape from my sight and went yee-ba-yeeba-andelay to her hiding place.

Then a few days later i saw another p3 girl at the hawker centre and she froze like a statue with her mouth gaping.

Just yesterday i saw a P6 boy at Plaza Singapura with his mummy and siblings. He tried to hide away from my by putting a plastic bag in front of his face. Doesnt that makes you more obvious to me?

but why do you need to hide from your teachers? can't you just say Hello Teacher? or Good-morning teacher?

I dont understand!