To switch to School Pool mode, please: Visit the "People" tab on the TPT School Express homepage by clicking on your profile icon on the top right of the screen and then selecting "TPT School Express".
Click "Manage Roster". Then, select "Switch to School Pool" on the bottom left of the "Manage Roster" modal. Confirm the switch by clicking "Yes, switch to School Pool".
Note: only Primary Admins can switch the distribution method for their school.