Content update: New exercises in Middle School Biology and Earth & Space Science

We've added exercises to our Middle School Biology and Middle School Earth & Space Science courses and removed a few others.

If you were already working in one of these courses, you may notice that your Mastery % has gone down. Don't worry, you haven't lost any of your work! Every exercise you've completed is still complete.

Your Mastery % is now being measured against a larger set of exercises, so the work you've already completed makes up a smaller percentage of the course.

Middle School Biology

• 11 exercises added

• 3 exercises removed

• Your Mastery % could decrease by up to 22 percentage points.

Middle School Earth & Space Science

• 12 exercises added

• 7 exercises removed

• Your Mastery % could decrease by up to 45 percentage points.

These are the largest possible changes. Most learners will see a smaller change, and some may not see their Mastery % change at all.

As you work through the added exercises and build your skills, your Mastery % will increase again.

One more change to know about

We've also updated how Mastery % is calculated across Khan Academy courses.

Your Mastery % now only counts the skills you've reached Proficient or Mastered in. Attempted or Familiar are no longer counted.

Because of this change, you may notice that your Mastery % has changed even in courses where exercises weren't added or removed. Some learners may even see their Mastery % increase.

If your Mastery % changed by more than the amounts listed above, this updated calculation may be why.

For more details, check out How is mastery percentage calculated?

We hope you enjoy exploring the added exercises and continuing to build your mastery!

Happy learning!