diff --git a/lib/questionlib.php b/lib/questionlib.php
index 9b47a4b3929..8371f3bc3e3 100644
--- a/lib/questionlib.php
+++ b/lib/questionlib.php
@@ -210,56 +210,16 @@ function question_context_has_any_questions($context) {
 /**
  * Returns list of 'allowed' grades for grade selection
  * formatted suitably for dropdown box function
+ *
+ * @deprecated since 2.1. Use {@link question_bank::fraction_options()} or
+ * {@link question_bank::fraction_options_full()} instead.
+ *
  * @return object ->gradeoptionsfull full array ->gradeoptions +ve only
  */
 function get_grade_options() {
-    // define basic array of grades. This list comprises all fractions of the form:
-    // a. p/q for q <= 6, 0 <= p <= q
-    // b. p/10 for 0 <= p <= 10
-    // c. 1/q for 1 <= q <= 10
-    // d. 1/20
-    $grades = array(
-        1.0000000,
-        0.9000000,
-        0.8333333,
-        0.8000000,
-        0.7500000,
-        0.7000000,
-        0.6666667,
-        0.6000000,
-        0.5000000,
-        0.4000000,
-        0.3333333,
-        0.3000000,
-        0.2500000,
-        0.2000000,
-        0.1666667,
-        0.1428571,
-        0.1250000,
-        0.1111111,
-        0.1000000,
-        0.0500000,
-        0.0000000);
-
-    // iterate through grades generating full range of options
-    $gradeoptionsfull = array();
-    $gradeoptions = array();
-    foreach ($grades as $grade) {
-        $percentage = 100 * $grade;
-        $gradeoptions["$grade"] = $percentage . '%';
-        $gradeoptionsfull["$grade"] = $percentage . '%';
-        $gradeoptionsfull['' . (-$grade)] = (-$percentage) . '%';
-    }
-    $gradeoptionsfull['0'] = $gradeoptions['0'] = get_string('none');
-
-    // sort lists
-    arsort($gradeoptions, SORT_NUMERIC);
-    arsort($gradeoptionsfull, SORT_NUMERIC);
-
-    // construct return object
     $grades = new stdClass();
-    $grades->gradeoptions = $gradeoptions;
-    $grades->gradeoptionsfull = $gradeoptionsfull;
+    $grades->gradeoptions = question_bank::fraction_options();
+    $grades->gradeoptionsfull = question_bank::fraction_options_full();
 
     return $grades;
 }
diff --git a/question/engine/bank.php b/question/engine/bank.php
index eb2a51230b5..dd25b246b70 100644
--- a/question/engine/bank.php
+++ b/question/engine/bank.php
@@ -56,6 +56,17 @@ abstract class question_bank {
 
     private static $questionconfig = null;
 
+    /**
+     * @var array string => string The standard set of grade options (fractions)
+     * to use when editing questions, in the range 0 to 1 inclusive. Array keys
+     * are string becuase: a) we want grades to exactly 7 d.p., and b. you can't
+     * have float array keys in PHP.
+     * Initialised by {@link ensure_grade_options_initialised()}.
+     */
+    private static $fractionoptions = null;
+    /** @var array string => string The full standard set of (fractions) -1 to 1 inclusive. */
+    private static $fractionoptionsfull = null;
+
     /**
      * @param string $qtypename a question type name, e.g. 'multichoice'.
      * @return bool whether that question type is installed in this Moodle.
@@ -309,6 +320,81 @@ abstract class question_bank {
         }
         self::$testdata[$question->id] = $question;
     }
+
+    protected function ensure_fraction_options_initialised() {
+        if (!is_null(self::$fractionoptions)) {
+            return;
+        }
+
+        // define basic array of grades. This list comprises all fractions of the form:
+        // a. p/q for q <= 6, 0 <= p <= q
+        // b. p/10 for 0 <= p <= 10
+        // c. 1/q for 1 <= q <= 10
+        // d. 1/20
+        $rawfractions = array(
+            0.9000000,
+            0.8333333,
+            0.8000000,
+            0.7500000,
+            0.7000000,
+            0.6666667,
+            0.6000000,
+            0.5000000,
+            0.4000000,
+            0.3333333,
+            0.3000000,
+            0.2500000,
+            0.2000000,
+            0.1666667,
+            0.1428571,
+            0.1250000,
+            0.1111111,
+            0.1000000,
+            0.0500000,
+        );
+
+        // Put the None option at the top.
+        self::$fractionoptions = array(
+            '0.0' => get_string('none'),
+            '1.0' => '100%',
+        );
+        self::$fractionoptionsfull = array(
+            '0.0' => get_string('none'),
+            '1.0' => '100%',
+        );
+
+        // The the positive grades in descending order.
+        foreach ($rawfractions as $fraction) {
+            $percentage = (100 * $fraction) . '%';
+            self::$fractionoptions["$fraction"] = $percentage;
+            self::$fractionoptionsfull["$fraction"] = $percentage;
+        }
+
+        // The the negative grades in descending order.
+        foreach (array_reverse($rawfractions) as $fraction) {
+            self::$fractionoptionsfull['' . (-$fraction)] = (-100 * $fraction) . '%';
+        }
+
+        self::$fractionoptionsfull['-1.0'] = '-100%';
+    }
+
+    /**
+     * @return array string => string The standard set of grade options (fractions)
+     * to use when editing questions, in the range 0 to 1 inclusive. Array keys
+     * are string becuase: a) we want grades to exactly 7 d.p., and b. you can't
+     * have float array keys in PHP.
+     * Initialised by {@link ensure_grade_options_initialised()}.
+     */
+    public static function fraction_options() {
+        self::ensure_fraction_options_initialised();
+        return self::$fractionoptions;
+    }
+
+    /** @return array string => string The full standard set of (fractions) -1 to 1 inclusive. */
+    public static function fraction_options_full() {
+        self::ensure_fraction_options_initialised();
+        return self::$fractionoptionsfull;
+    }
 }
 
 
diff --git a/question/engine/simpletest/testquestionbank.php b/question/engine/simpletest/testquestionbank.php
index 4610f90d93c..697a7a69381 100644
--- a/question/engine/simpletest/testquestionbank.php
+++ b/question/engine/simpletest/testquestionbank.php
@@ -58,4 +58,34 @@ class question_bank_test extends UnitTestCase {
             'frog' => 'toad',
         ));
     }
-}
\ No newline at end of file
+
+    public function test_fraction_options() {
+        $fractions = question_bank::fraction_options();
+        $this->assertIdentical(get_string('none'), reset($fractions));
+        $this->assertIdentical('0.0', key($fractions));
+        $this->assertIdentical('5%', end($fractions));
+        $this->assertIdentical('0.05', key($fractions));
+        array_shift($fractions);
+        array_pop($fractions);
+        array_pop($fractions);
+        $this->assertIdentical('100%', reset($fractions));
+        $this->assertIdentical('1.0', key($fractions));
+        $this->assertIdentical('11.11111%', end($fractions));
+        $this->assertIdentical('0.1111111', key($fractions));
+    }
+
+    public function test_fraction_options_full() {
+        $fractions = question_bank::fraction_options_full();
+        $this->assertIdentical(get_string('none'), reset($fractions));
+        $this->assertIdentical('0.0', key($fractions));
+        $this->assertIdentical('-100%', end($fractions));
+        $this->assertIdentical('-1.0', key($fractions));
+        array_shift($fractions);
+        array_pop($fractions);
+        array_pop($fractions);
+        $this->assertIdentical('100%', reset($fractions));
+        $this->assertIdentical('1.0', key($fractions));
+        $this->assertIdentical('-83.33333%', end($fractions));
+        $this->assertIdentical('-0.8333333', key($fractions));
+    }
+}