Let's say we have a few sentences and we put them in the proper category, elementary, pre-intermediate,

intermediate etc. What can we call this activity? Is it levelling sentences or grading sentences?

I have to level / grade these sentences.
This book has so many levelled / graded sentences.

Are both OK?


More generally you're classifying the sentences. More specifically you're grading them or rating them by level.

(You're not leveling them.)