1) Achievement levels 2) Attainment levels 3) Flattens 4) Flattens out 5) Grand Canyon vistas 6) High spots 7) Levels of achievement 8) Levels off 9) Mesas 10) Starts to stagnate 11) Stays constant for a while Found on https://www.crosswordclues.com/clue/plateaus
1) Achievement levels 2) Attainment levels 3) Flattens 4) Flattens out 5) Grand Canyon vistas 6) High spots 7) Levels of achievement 8) Levels off 9) Mesas 10) Starts to stagnate 11) Stays constant for a while 
• (pl. ) of Plateau