Where are the other kids?!!
My first thought is lack of parental advocacy combined with teacher awareness.
Maybe there are G kids who are bored and under achieving so they are not being recognized as enrichment-ready. On the other hand, maybe there are the high achieving kids whose parents think "oh, everything is ok - she's getting all As" so they don't advocate for enrichment.
Who knows. You mentioned that the pre-algebra program was your DS's choice, so I think it's a good place for now. If he wants to be there he's more likely to get the most out of it.
He sounds like my DD9/Gr5
She's not a prodigy either and has very strong language skills (early reader, etc), but she loves math too.
I wouldn't worry as much about the normal classroom experience (although it is important and a good thing to have) because I think if there's a curriculum mismatch it can stressful for the student regardless of the classroom experience.
Fyi, my DD9 was a pioneer as well - she was in a pilot program in grade 3/age 7 for a junior math enrichment program. She loved it. Unfortunately the program was cut the following year due to funding, so she had to wait for grade 5 when the regular version of the program began.
