Yes your classes will decrease as soon as the leading pet completes his classes.
To make it easy on yourself, if you have more than one pet in Level 10 make sure you set them up like this:
If your leading pet has 50 classes to go, and you have other pets in Level 10 also working their way up, set them up this way (or use this guide for however many classes you need to do):
- stop your next closest pet at 11 classes to go
- stop the 3rd pet at 21 classes to go
- stop the 4th pet at 31 classes to go
- stop the 5th pet at 41 classes to go
When your leading pet completes its 50th class, then go to the next pet waiting at 11 classes. You can graduate him immediately because he will drop to 1 class left after your leading pet graduates, and you will just need to do one class. In addition, all the other pets will also reduce their required classes by 10.
If you graduate them in order from the pet waiting at 11 classes first, you will pass every pet at once since their required classes will all consecutively drop to 1 as you move ahead!
I did this with Weight Training and Painting and finished the entire shebang in one day

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