No, when you add a new student to Educake, no quizzes will be automatically assigned to them. (This has changed - previously, any quizzes set to a class that academic year were automatically assigned to new students.)
Here's how to add an individual student to a quiz you've already assigned their class:
1. Click on the quiz
2. At the bottom of the results grid, click "Add Students", like this:
3. Click "Add to quiz" next to the student you want to add
When you click "Add Students", you'll see a list of students in the class who have not yet been assigned the quiz. Click the blue "Add to quiz" button next to their name if you'd like to assign it to them, like this:
4. That's it!
If you refresh the page you'll see their name added to the results grid, and the student will see this quiz the next time they log in to Educake.