While your students are working on a Practice assignment you can view their progress by navigating to the Assignments page and clicking the "Performance" button next to the specific assignment.
On the Performance page for that assignment, you can see each student's progress towards mastery right next to their name, under "Overall Grade." Further to the right, you can see how far each student has advanced through the specific topics that make up the Practice assignment. See the key in the upper left side of the screen to determine how much progress each student has made.
In this example, the three students have mastered the topic "Identifying Conjunctions," and they are part of the way through "Using Coordinating Conjunctions" and "Using Subordinating Conjunctions. The students are 13-14% of the way through their assignment.
Note that Practice assignments are graded based on the percentage of assigned topics that your students masters. On a single topic, the student's mastery score suggests his or her progress toward proven understanding of that concept. A score of 88, for example, does not mean that a student has answered 88% of questions correctly; rather, it means that a student is 88% of the way toward achieving mastery in that topic.
A student will not earn a 100% on a Practice until he or she has mastered all topics that make up the assignment.