Thank you very much for your answer. What you say really makes sense. In fact, it had already crossed my mind that something like this might be going on, but I thought I was probably exagerating since my son doesn't even look gifted right now.
Unfortunately, our options are limited. We live in Europe and there are not gifted schools in our country. Our choices are basically enrichment or grade skipping within a normal school, and I think DS is still too inmature for acceleration (he can be adding hundreds in his head one minute, then the next minute throw a tantrum because his balloon popped).
I don't really know how we will cope, but after reading your message I will make finding intellectual peers for my son my top priority, so he can understand he's not alone.
Meanwhile, I will continue in the forum reading your messages and learning from you and all the others!
