school2.clj

(ns school)

(defn grade [school grade-num]
  (get school grade-num []))

(defn add [school name grade-num]
  (assoc 
    school 
    grade-num 
    (conj (grade school grade-num) name)))

(defn sorted [school]
  (let
    [sort-by-grades 
     (partial sort-by key)

     sort-students-by-name
     (partial map 
              (fn [[grade students]] 
                [grade (sort students)]))]

    (into 
      {}  
      (sort-students-by-name
        (sort-by-grades school)))))