He is in the same year as my older brother.
Tofugu not only has fans in early elementary school, but also elderly fans over 100 years old.
One third of the third grade threw up after school lunch.
Your study year is kind of like the years you've studied. Where do you study? School. What is a year of study in a school? It's your school grade.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.