Does English or maths suffer
Yes, it certainly can. Well certainly with English - if you consider it they are less exposed in school to it - vocabulary can be less broad (which could be counteracted if they read a lot at home). Also, with English, if your child might have a difficulty (such as dyslexia) it can be really difficult for them. Maths can be a struggle anyway, but through Irish it might be harder especially if you can't back it up at home (knowing the terms in Irish etc) Also if they go on to a secondary school which teaches in English then they will have a spell of having to relearn terms. (This can happen in subjects even if they go to Secondary school and then move to third level.)
Are the children usually more driven seeing as it was a conscious choice by the parents?
No.
My family consider the Gaelscoils extremely snobby, I can't understand this as they are not fee paying...
Can be, not sure I'd say extremely, I think the level of snobbery depends on the area. What might give you the answer is to ask yourself why do you want them to go? Is it because you think it's better or for other reasons? Do you think it's important that Irish is used everyday
Please tell me about irish speaking secondary schools. Do children who go to the Irish secondary schools generally get more points.
I don't think so - but they will get a % for doing the exam in Irish, so that helps! On a side if they go to an English speaking secondary school you will find that whilst they will do well in Irish lessons their grammar might not do so good, You will have to keep an eye on that throughout primary - it's like using everyday English - they grammar might be off
Remember, if your Irish isn't great you will find helping with homework hard. This may have more of an impact than you realise. All their reports will be in Irish and all their performances will be too.
Also, Irish schools are often the 'best' (performing) because any child with extra education needs don't tend to go there or leave to go to another school that can facilate them