It's good to know that you're having a good experience with QuickBooks, Reach1.

Yes. You'll have to modify the item manually. All payments will be posted to the account you've assigned to the product. 

You can do this by going to the Item List page. Let me guide you with these steps:

1. From the Lists tab, select Item List.
2. Double-click the Tuition Fee item.
3. On the Account field, select the pre-paid account.
   
   
4. Click OK.
5. In the Account Change page, select No.

As for your second question, we're unable to create an invoice in bulk. Rest assured, I'll take note of this idea and share it with our developers.

If you want to send a reminder message to your customer

of the upcoming invoice due dates, you can check this reference: Automate invoice reminders in QuickBooks Online.

Feel free to mention my name if ever you need help. Have a safe Christmas!