RCM: Should I skip from grade 5 to grade 7?

I have no idea what instrument you're talking about but my experience (with b and guitar) on skipping grades was no grades for 4yrs then straight to 6 then 8 the next year on them both. But I'm guessing there are books for each of the grades which outline exactly what's included in each grade? So you need those books. I'd recommend you get, say 5, 6, 7 and 8 maybe later. See exactly what's in them then decide. Also this was for b and guitar but the jump from 6-7 was huge compared to the jump from 7-8. So maybe you could jump from 5-6 then 6-8, I don't know, it all depends on your skill and effort. But (I'm guessing) there are books which have everything you need to do so find them.