One of the big differences is just the size of the schools. I was in Ireland for 8th and 9th grade. The school I went to consisted of grades 6th-12th with a total of around 300 students, with 48 kids in my grade. My graduation class from high school back in the US was around 600. My high school consisted of 10th-12th grade with around 1800 students total. This difference in size makes a huge impact in the different cultures that have evolved in the different school systems.