A Catholic school in Melbourne's south east has threatened to bar students from a casual clothes day unless their parents sign letters opposing the Turnbull government's school funding changes.

The move has infuriated some members of the tight-knit St Elizabeth's School community, who have accused the Dandenong North school of political interference and intimidation.

Only Romania and Turkey were ranked below Australia in education in the latest UNICEF report card. Credit:Michele Mossop

It also prompted federal Education Minister Simon Birmingham to phone the school on Friday to inform it that it would receive an additional $5.9 million of federal funding over the next decade.

On Thursday, students at St Elizabeth's were sent home with letters that said the federal government's Gonski 2.0 plan could lead to higher fees at Catholic schools and cuts to programs.