There are several reasons why your class' score is not being counted:
1. The students should be playing on the contest activity. On the student homepage, they will see the title of the contest in the green panel on the left hand side. If this isn't showing - for example, if a different activity has been chosen - their scores won't count. To change this, click the panel and select the contest activity.
2. Students must have completed the welcome phase to see the contest.
3. At least ten students must participate in the contest for their class score to be counted on the leader board. If less that ten students from an entered class participate, the students who do take part will still qualify for the individual student leader board and will still receive their participation reward.
4. Each student can answer a maximum of 1,000 questions in each contest. Once they reach this 1000 limit their scores will stop being counted. This is to make it fair for schools that don't have good access to computers, and students who can't log in from home.