Over and over again with beginners - not all, just some, and not necessariloy little ones, I have this problem with adults as well - when we learn triple time they're fine as lonmg as we have either three crotchets or one dotted minim in the bar. But when the rhythm is minim-crotchet, whether this is for several bars at a sdtretch, or just one bar in the middle of the piece, they just can't get it. I have treid everywhich way, getting them to clap back rhythms, having them count the beats slowly and carefullly, singing the song to get used to the sound of that rhythms, working with and away from thw written out rhythm, emphasising the fact that the crotchet leads straight into the minim (three-ONE over and over) but some just get wedged on that final critchewt and can't move off it in time.
I'm not so much asking for suggestions as for a reassurance that everyone else also finds a significant minority of their pupils can't do it either. Sometimes I jast have to leave the piece where it occurs and come back to it when reviewing maybe even months later.
I have one particular little boy who's 6 and whose parents seem to think he's bright - can't understand why I say his counting is so dire in music because he is supposed to be "exceptionally good at maths". Yeah, this would be why sometimes when he has three repeated notes he plays two, and vice versa, right? (I don't actually say the counting is dire, btw, just that we still have to improve it). Oh, he can clap a minim followed by a crotchet all right. Followed by about a nother minim's worth of rest or hanigng on the the last note.
I know sometimes it's b ecasue they can't get rid of this 4/4 feeling they've played so much; I play strong waltz rhythms on the piano for them to play against. Still doesn't do it.