What information is given for each data point?
On the line graph in History for an individual student, each data point has a shape. There is a diamond for the Baseline test, a triangle when you chose Test Incorrect, and a circle when you chose Retest All. If you hover your mouse over a point, it gives the date and time that the test was given, the number correct, and the percent correct.
If you have All Students selected, it will only show Average Correct instead of a type of test.
If you are using purple Managed Subject Tabs created by an Admin Account, the administrator may have selected all tests to only test one way (Test Incorrect or Retest All) instead of having a choice.