Instead of 10 favorite teenage albums, I'll list 3 albums that really disappointed me when I was still in school:
1) Television, Adventure - Quite a nice album, but Marquee Moon had been such a stunning visionary triumph that this one was (and remains) a letdown.
2) Elvis Costello, Trust - I had thought his first 4 albums (plus an odds and sods collection) were great, almost like Dylan fronting the Beatles (plus 60s organ). This one was labored and uninvolving, which is how I've also felt about almost all his subsequent work.
3) The Who, Who Are You. - The Stones had already successfully responded to the punk / new wave movement with Some Girls. Townshend seemed sympathetic and ready to do it too. Plus I had quite liked (unlike most fans) their previous album, the deeply depressive and singer-songwritery Who By Numbers, and I had also found his contributions to a joint album with Ronnie Laine quite delightful. This one I found to be a tedious waste of time, decisively ending his career as an interesting artist.