If you are in an organization that sells courseware, you will likely have contracts with your customers for the work.
One project’s contract required all the work items originally listed, and the customer wanted them in lesson order, so prioritization was predetermined. In that case, there was no grooming the backlog by prioritization. We just split up the stack of work items into iterations. Easy peasy.
If you have influence over the contract, we suggest that you bring up prioritization early in the customer meetings and get their buy in. Countless times the SMEs or stakeholders will change their mind on what they want as they start seeing it come together.
You can still offer fixed prices if your contract allows prioritization. Then the highest priority items make it in scope and the lower priority items may not.