so you need to ask them more - are they talking aspergers 'different'? adhd 'different'? sensory processing disorder 'different'? what makes him 'different' from his peer group in their eyes?
if he's divergent and original, he's obviously a bit quirky - is he extra-bright quirky? (so not meeting his potential because they aren't providing the necessary stimulation - would an ep assessment help to quantify whether he needs further extension work?) or is he having difficulties managing the social interaction aspects of the classroom, which is causing him not to reach his potential - would an iep with social targets be more beneficial rather than academic targets...?
i don't know your son from adam, so have no idea what support they are giving him/ targets they are setting. what are the targets they have currently set - are they solely academic, or more social/ process driven? does he have any issues with handwriting/ fine motor tasks which could be causing him to work slower? does he have aproblem following the rules of the classroom? does he interrupt the teacher to answer the questions when it isn't his turn? does he refuse to answer any questions at all even though the teacher knows he knows the answer? is he responsive? does he have friends and a similarly able peer group?
(i'm not pointing in any direction in particular btw, just throwing out q's in an attempt to work out why they believe he still needs to be on the radar)
fwiw one gp told me that ds made the hairs on the back of his neck stand up. i assume not in a good way, but he didn't really elaborate, so i do know professionals can be reticent to discuss or suggest specific diagnoses. and it took 2 years for the paed to admit that dd2 had cerebral palsy - very common to call everything 'developmental delay' for as long as possible...
do any nof those questions ring any bells? there are loads of other reasons they might wabt to keep him flagged.
as an aside, what are you worried about? what actually concerns you about him being given extra support via an iep? (nosy)