Shadowbolt Academy

Inspired by some stories that featuring characters that actually join Nightmare Moon's Shadowbolts:

Captain Fluttershy first appears in Stryke's Random Elements, [link] and then appears with Lightning Dust and Cloudchaser in the sequel.

Ditzy Doo (aka Derpy) and Shining Armor become Shadowbolts in Trinary's Rainbooms and Royalty, [link]

Technically, Ditzy and Shiny had different uniforms (as well as certain... alterations that I won't spoil), but for this picture, it made sense for all six to resemble each other.

Rainbow Dash is from Luna Eclipsed, minus the stitching on her costume because I thought it looked better this way.