It's tough. My 11yo is sometimes reluctant but luckily he doesn't refuse to take - just avoids until he is reminded.
I second finding someone who has personal experience of Adhd with and without meds who can explain any benefits, plus any side effects.
Different medications do different things so it might be that the one currently prescribed doesn't help so it's trial and error to find the right one.
Mostly, don't see the medication as a cure for all his lack of concentration etc snd ensure he isn't getting into trouble at school for things he cannot help, without strategies as well as medication being out in place.
Eg my son takes his medication but is an appalling time keeper. So he has reminders set on his phone to come home when playing out, or to take his top up med on club nights.
We have systems in place for organising school work and his bedroom. The medication doesn't stop him being an untidy bugger, just helps him not take such risky behaviours to achieve the dopamine high that he would otherwise need.
Find famous people he can look up to - Simone biles was one for my youngest dd when she got her Adhd diagnosis (Dd is currently unmedicated).
Justin timberlake, Michael phelps, Ty Pennington, Will.I.am amongst many others.
I'm a parent to 2 Adhd children who has recently been diagnosed with Adhd myself, also working as a send ta. It will always be a challenge for him to want to be seen as normal - particularly a thing I've noticed with teenagers.
Maybe compromise and ask him to take them certain days and not others - for a while our son took them mon-thurs and had a break fri-sun. It worked when he was at football training Friday nights and was busy charging around on his bike at the weekend. But as school demands increased and his extra curricular activities changed, he found it harder and harder so agreed to go back on full time meds. He now doesn't have a break at all, even during holidays as he is currently unable to self regulate, even on his current dose.
Reassure him that taking medication is ok. If he had a broken leg he would need crutches to help him, same as if he had a headache he would take painkillers to help. Medication helps ensure he receives the dopamine his body produces effectively, without it he may take riskier and riskier actions to achieve the same 'high' a 'normal' person would get.