Sometimes I have to wonder if one year really makes all the difference.
From my observation, people holding the same position, at a different age (one is one year younger), receives different amounts of respect.
This, for me, is a little bit ridiculous.
If he's given a particular position to hold, then it's likely that the higher-ups place good faith in him. People shouldn't doubt him because of his age, nor should they doubt his ability. Because, in the end, it was the consensus that he was the most suitable.
If you doubt him, do you think you can do better?
Sorry, but the answer is very likely to be 'No.'
And thus, listen to him. Respect him. He is the leader. You are the follower.
When first appointed, you all had no qualms. And that's the way it should remain.
It does not mean you are given privilege to slack around because you are his friend, or classmate, or someone who's older/same age as him.
By rank, he is above you.
It's not about acceptance, it's obedience.