How are classes in america different than ireland?

I'm confused on the subject of classes in America and other countries. In Ireland we use 1st class or 1st year (secondary school). What's the bloody difference?? I want to know!!

America is different than Europe in quite a few ways it seems. I am still confused about the European system of education, but in America it is broken down into two to three parts. At age 6-7 children enter into grade 1 or First grade which is simply called "Elementary School". After grade 5 there is usually a change of schools to "Middle School" or "Junior High" This is sometimes skipped and the middle grades 6-8 are split between Elementary School and High School. High School is the final step in basic education which covers grades 9-12 and usually has teens graduating at ages 17-18. Then higher education can be sought in a few forms, College or University. College usually offers associate's degrees that specialize in trades or a concentrated field of study. Universities like Stanford, UW, UCLA, and Harvard offer a rounded and more intensive form of higher education that expands on the basics and adds one or more focus studies (or majors and minors).

Hope that helped.