Lithuanian schools in up to about 1998 (might be wrong on exact year) had same system, then it was changed to 10 grades, but the lowest grade - 1 was ever used as a disciplinary action. Lowest you would get for failing assignment or homework was a 2. But even when it was 5 grade system the 3-, 4+ or 5- was quite regular occurrence and depended on teacher and subject mostly, as +/- were not accounted officially so 4- was exactly same as 4 for the final grade of a quarter/trimester.

A few of my teachers who'd used +/- signs added them to differ between a strong qualification of work to the grade and a one step for higher/lower grade respectively, i.e. 3- converts to "almost 2", which is just a written clarification.

I saw once a 2+!