別: distinction; difference; different; another; particular; separate; extra; exception.
The school will hold an exam (a competition between classes), where the 2nd grade student will pair up with the 1st grade student, and the homeroom teacher was explaining the rule and the outcome (some kind of rewards and punishments for the winning class and the losing class). The above-mentioned sentence is the opening explanation.
What does it mean the 学年別における on that sentence? For a different academic year (sounds odd)?