Connect a new Microsoft account to Minecraft?

My little brother bought Minecraft with his school Microsoft account. But he can't go into multiplayer. Is there a way to change his Microsoft account or change the account so that he can play online?

Moin, Minecraft is a game and definitely not part of the class. Games are probably blocked in the school account.

He can set up one himself on his house PC, with luck it works. Otherwise, speak to the teacher so that she can delete him from the school account.