You shouldn't track favours with your friends with money. You should both be well into the green, so who exactly is benefiting more doesn't matter. The costs your friends impose on you should be so much lower than the benefits that asking for compensation is genuinely insulting outside very special circumstances.
A key feature of narcissism is false intimacy. Such as allowing a stranger to impose a cost on you without paying for it. The narcissist has a very twisted relationship with attachment, typically having boundaries that include everyone. "Everyone is identical so everyone is me." It would be weird not to be intimate with yourself.
At school, you don't pay and don't get paid. As if you're in an intimate relationship with your school. As small children (say, before 8) should indeed be in an intimate relationship with their caregiver. Except, of course, you're extremely not in an intimate relationship. School isn't in the least bit interested in letting you impose costs on it, and will react to even minor transgressions with extraordinary violence, just like an insecure government does.
The school is intentionally designed to model narcissistic sociology. Encourages you to destroy or disregard your boundaries.