The phrase "achievement spectrum" refers to a range or scale of different levels of success or accomplishments that someone can have. It represents the full spectrum or variety of achievements that individuals can attain. Full definition
So there is an issue: traditional ways of organising and delivering school education are sometimes failing students at both ends of the achievement spectrum. (teachermagazine.com.au)
Dozens of other NCLB critics have reached similar conclusions, and scads of proposals for that law's rewrite offer remedies, such as including more subjects in the accountability system and giving schools credit for student growth across the achievement spectrum. (educationnext.org)
Rather than focus exclusively on ensuring that kids are minimally proficient, we can now reward improvement across the achievement spectrum. (educationnext.org)