Tens of thousands of Victorian Catholic school students have been sent home with letters warning their parents against voting for the Greens in next week's federal election.

The Catholic Education Commission of Victoria has circulated the letter to schools in marginal seats, seats where MPs are retiring and electorates where the Greens are hoping for a win.

These include Batman – which the Greens hope to pick up thanks to its rapidly changing demographic– and the Greens-held seat of Melbourne. The letters were also stuffed into school bags in Wills, Corangamite, La Trobe, Bruce, Chisholm and Dunkley.