The full extent of the windfall for Catholic schools under Prime Minister Scott Morrison's funding "fix" last year has been revealed in documents that show the sector will receive more than $4.1 billion in additional federal funds over the next decade.

Official spending projections also show independent schools will gain $263 million in extra federal funding over the same period - in contrast to earlier fears they could lose up to $2 billion as a result of the changes.

Prime Minister Scott Morrison and Education Minister Dan Tehan in Canberra last year. Credit:Alex Ellinghausen

The main element of the package announced by Mr Morrison and Education Minister Dan Tehan in September adjusts the way a school's wealth is assessed, meaning it will now be determined by the income tax paid by its parental cohort.

That reform - for which the Catholic sector lobbied aggressively - will generate a $3.4 billion windfall for Catholic schools by 2029, according to Department of Education modelling.