my dad being military I moved several times while I was younger, and then I and my brother joined the military and moved many times as well, so I've seen a lot of kids in this situation.

I never noticed any problem with kids moving in middle school or younger, no matter how many times they moved it was pretty easy to make new friends at school and church. My brother had a daughter though who moved three times during her HS years and that was pretty rough (although she was kind of happy to move the third time as she had nothing really keeping her at the second place).

it kinds of depends on how often you move as well. we and our kids did get used to moving, so you learn adjustment strategies. a kid who's never moved before and is uprooted for the first time in 8th grade may have a lot different response than ours did.

we just moved last year within San Antonio, and had two kids going into Junior year, so we mostly focused on houses in the current HS boundaries, but my boys were kind of accepting and seemed like they would've been ok going to a new HS for the last 2 years.