any suggestions for grades 5-8

or one difficult part and the other easy/easier

Peters Edition do things like the complete Beethoven Symphonies for piano duet. All depends what style the players are into, and whether it's a major undertaking or a shorter piece that is being looked for...Dover editions might do a variety of this sort of classical arrangements too.

ALSO: Th ABRSM Haprpsichord etc. syllabus includes Ensembles, which include PIANO DUETS!!! How many of us have come across this I wonder! I've got a copy of the 2003 syllabus and it has a good number of duets, in three standards: 4/5, 6/7, and 8 (called Primary, Intermediate and Advanced). Worth a browse for lots of ideas!

(Posted this reply on other thread first)