schools for expats (Dublin)

planning a relocation to Dublin. BIG Problem is that the schools that are in the top 20 are all full, waiting lists as long as 3 years. So my question is if you are an expat in Dublin and your high school age children attend a government school what is you experience with that? Is it an easy transistion from a school in the US for example? Is the quality of teachers good or better than the average US school?
Any thoughts would be very helpful.
Thanks
M