No once they sign for a club in England they cannot play schoolboy football in Ireland. They can, with their clubs permission go on trial and play trial matches in Uk but there is also an option for a lad to sign forms of intent with a club in Uk but still play in Ireland as he has not actually signed for UK team but just a form of intent to sign at a later date but this is not binding. Hope this is not confusing and to be honest there are ways getting round things but to my knowledge this is the UEFA Regulation.