Trocaire Poetry Ireland Poetry Competition 2014 - see here Theme: It's Up to Us! Primary and secondary school categories (and there's an adult category too). Deadline
RTE Guide Puffin Children's Short Story Competition 2014 - see here - three different age categories with different word lengths. Deadline 11th April 2014.
Windows Publications 22nd National Poetry Competition 2014 - see here Primary and secondary school categories, and an Irish language category. Deadline 18th April 2014.
And another - this is a very big UK competition (7,478 entries last year).
Foyle Young Poets Award 2014 - deadline 31st July 2014. Ages 11-17, more details here
So, write under 18's, write....