"evidence of attainment" is not something included in my districts TTESS Student Learning Objective.

Easy goals are staring you in the face in the TEKS. They are even phrased in "we will" or "the students will" styles that our objectives are asked to be in. For instance the middle school TEKS for 2: music literacy reads, "The student reads and writes music notation using an established system for rhythm and melody". Use that statement and think of a way to evaluate students within that statement. How would you test a kid to see if they can read or write music? (This doesn't mean compose with legitimacy, it literally means taking pencil to paper or Noteflight in any capacity). And more importantly, how can their ability to read or write be measured to track progress? English classes do this exclusively.