I am not sure when the school teaches Roman numerals. Obviously it wasn't third grade because my DS10 has not learned anything about it (He's going on fifth). However, DS8 "just know" them when he picked the third grade math topic on Roman numerals on IXL to work on last night. We were all surprised and asked him where he learned it? Videos? School? Books? He said no to all of them but could not tell us where else. This kid just surprises us like this :-)

Oh, he was also 72% complete on the 8th grade geography on Oceans and Continents on IXL last night, before going to bed.
This doesn't surprise us though because he memorized the world map since he was five.