I think Gaelscoils are more open and inclusive nowdays, but that wasnt always the case.
My brother attended a gaelscoil primary school 20 years ago - parents thought it would be good for his education. Turned out to be a big mistake. Whereas my brother had no difficulties with the language - he is still fluent to this day and got an A in honours in the Leaving Cert - the school was a nightmare. Parents sent him to an english speaking secondary school.
The gaelscoil he went to (which is still around) was an established one. At that time, the majority of the kids were from Irish speaking families i.e. speak Irish all the time at home - parents were from the gaeltacht. The minority of kids from non-Irish speaking familes were treated as second class citizens - teachers looked down on them and regarded them as less than dirt and over time, the gaeltacht kids picked up on it and you got what can only be described as an appartide situation whereby the non-Irish speaking family minority got a very hard time on all levels. There was a very anti-Dublin attitude. Though the kids from the Irish speaking families were born and bred in Dublin, they were brought up with the view that anything from the west of Ireland is good & anything from Dublin is bad. If my brother said cheered for Dublin in a GAA match, he would get a hard time from the other kids, thought they were also born in Dublin - bit like the complaints in England about English born spectators at cricket matches in some places cheering from Pakistan against England.
Brother also said the standard of teaching was poor - gets masked by the fact that the Irish educational stream is generally separate from the English and it is difficult to compare the actual standard in exams for papers answered in each language - generally exam papers in Irish will get marked easier (in addition to the extra 10%). Took him c.1 year to catch up with english speaking students when he switched to english speaking school.
I dont know what the schools are like now, but hopefully they have changed.
One thing to look out for is that the Irish requirement for entry into some universities will be dropped soon - it is against EU laws because applicants from all EU countries must be treated equally - cant have a requirement that Irish people need LC Irish to go to college, when it isnt a requirement for e.g German applicants to the same college. Also, my wife is a secondary school teacher & says that there are rumours going around that, due to the influx of foreign people to Ireland and anticipated future public demand (as well as the aforementioned EU reasons), Irish will be dropped as compulsory LC language sooner rather than later. 10% bonus is also likely to go to if challenged in court - try justifying giving an Irish speaking university applicant 10% extra marks than an english speaking one when both apply to do a course thought entirely in english. Kids starting gaelscoil today are unlikely to be able to avail of the bonus marks etc by the time they are LC age.