If it makes you feel any better, neither DH or I came close to National Merit Semis even though we excelled in everything else (SATs, grades, college acceptance). Like, individually, we had these weird blocks when it came to PSATs. I took the PSATs from 9th -12th grade and did comparatively badly each time.
I know you're licking your wounds and you know that it doesn't matter in the long run, but I just thought it'd help to hear about two others who also just didn't shine when it came to National Merits or the PSATs.
