Personally I think (as both parent and educator) that grades of both kinds are massively over-used. We don't have a grade point average equivalent here, but even so, there are too many grades. There's plenty of evidence that they impede learning, e.g., people take much less notice of the actual content of the feedback they get - the useful stuff, the stuff that tells them how they could improve - if it comes with a grade.
If you have to have one or the other, I'd rather have grades on achievement, because I have no confidence in any teacher's ability to judge effort reliably. I might feel differently, though, if I had a child who tried hard but could only ever achieve modest achievement grades.
DS gets grades for effort, progress, presentation and organisation in every subject every half term (if I've got that correctly). They've been exemplary so far, but every time, I recap the conversation about them being just fallible indicators and not important in themselves, and ask him how he thinks his work is going.
