you can always roleplay that 17 years prior the spartan king and the athenian aristocracy gathered to discuss some stuff and after being pissed by the philosophers making fun of him in a witty way he took his revenge by pissing on the wrong cup aka as the athenian leaders wife and thus after seing their son he feels a bit "fatherly" towards the kid and challanges him to participate in the agoge

or ofc you can always create one hell of a mess in the midle of the discussions about the future of the league getting the spartans all spunked up calling the athenian weakling cowards and the athenians and rhodians calling the spartans no better then filthy stinky barbarians and from then on role play that they made a bet and that poor kid will have to pass on the agoge or the spartans abandon the league but if he passes the spartans must respect the league "democratic" ways and stop making powerplays to grab the leadership