A schoogie is a term adults use as a euphamism when speaking to children about dried nasal secretions (aka - boogers, snots, etc.). They often think that other adults will believe their children to be more cute and less vulgar than other children, but when this term is used at school the child is looked upon as a creature from Mars.
Don: Jimmy, gross! You have a schnoogie hanging from your nose!
Jimmy: A what?!?
Don: You know, a booger.
(All children stop looking at Jimmy and stare at Don wide-eyed)