ZipGrade can easily read blue and black pen and pencil. Be sure to have students fully color in the circle with as few stray marks as possible.
When students are using pen and make an incorrect mark, liquid paper works well to make corrections; but correction tape is even better. (https://amzn.com/B001LDKAVE)
In the case where correction tape is not available or you allow students to 'cross out' an answer, you may always override how ZipGrade interprets an answer:
- Within the mobile app select the quiz from the list of quizzes.
- Then press the 'Review Papers' button
- Select the paper to edit
- Select the menu in the upper-right corner and select 'Edit Answers'
- Toggle the blue 'X's to show which circles should be considered dark
- On return to the paper list, the paper will be regraded
This change may also be done immediately after scanning the paper by pressing the 'Review' button.
Also, I'd recommend prompting your students to make a mark in the margin with the question number that they have crossed out so it's easier for you to find these issues when scanning. Obviously, correction tape puts the responsibility more on them and is less work for you.