Anecdotally, I feel like I had an EF nadir as a child at around 10-11. I had a lot of trouble forgetting completed homework or books I needed at home. My friend had a similar experience with her GT son at 10-11 apparently having more problems keeping track of assignments and things that needed to be taken to school or practices. I don't know if this was a true nadir or just lagging behind increasing demands in EF, but in both cases it dramatically improved in a year or two. Maybe this corresponded to the 12 yo time period you are proposing?
