Rebuild the missing context
Assume the recipient will not remember every date, promise, or earlier conversation. For a message about how to apologize for excluding another student, use this factual base: name the assignment, rule, person, or shared work affected and do not conceal the extent of the problem.
Say what needs to happen next
State the decision, information, or practical action you need and include a real deadline only when one exists. Ask which repair is permitted, complete your own work, and accept a fair academic consequence. Make the immediate next step clear enough that the recipient can answer without reconstructing the entire history.
Avoid making urgency into pressure
Do not pressure a teacher or classmate to erase a consequence or support a false account. Report bullying, threats, abuse, and safeguarding concerns to a trusted adult or official school channel. Do not make the other person responsible for reducing the discomfort that prompted you to write.