Dear Ania,
I know you asked Mary about grade skipping, but I'll offer my two cents as well. My son is 11 and skipped 5th grade last year to go to sixth. This year he's in 7th. He is also small, thin, and young (a late summer baby). He said skipping was the hardest thing he's had to do, probably because it coincided with a change in schools (from elementary to middle) and suddenly he's immersed in a whole new setting where everyone can see how little he is. I should have skipped him in elementary school (I read somewhere the younger the better). Both his younger brothers were skipped younger (2nd and 4th grades). BUT (big BUT), my son gets all A's and is clearly at the top of his 7th grade class. He is better challenged, although he still considers a possible additional grade skip. I asked him recently if he could imagine being a sixth grader this year, and he gasped, "NO!" Even if he is outsized, it is clearly a superior situation for him. He gets along with older kids better (I think his classmates are still too immature for him!). My advice--the sooner the better!