Ningun/Ningunas Singular/Plural

Question

Hola
Please explain why the sentence:
"Ningunas gafas me quedan bien" uses Ningunas and yet the sentence "Ningunos ninos de mi colegio llevan reloj" is incorrect even though both sentences have plural nouns and plural forms of the verb to agree with the nouns. 
Un saludo

Silvia Píriz · Accepted Answer

Hola E. L.
The difference is that gafas is a noun commonly used in the plural to refer to a single object (a pair of glasses). This allows us to say:
Ningunas gafas me quedan bien. – No glasses suit me.
However, niños is a regular countable noun, and Spanish normally uses the singular ningún in negative constructions, even when referring to several people:
Ningún niño de mi colegio lleva reloj. – No children at my school wear a watch.
So, although both nouns are plural in your examples, they follow different usage patterns.
I hope this clarifies the distinction!
Silvia