Most schools teach in English and teach Irish as a second language. Irish is rarely used in normal day to day interactions and never at work unless you work in an Irish language related area or government department that supports Irish as an official language.
There are some niche exceptions:
- "All Irish" schools where you optionally learn through Irish
- "Gaeltachts" which are pockets of Ireland where Irish is promoted and spoken. Even here the locals will happily switch to English if you prefer.
I like Irish and wish it was more widely spoken as an everyday language but in reality you have to make an explicit effort to experience it.