Pitch Matching

I am working with Vista students with their songs for Winter Sing next week. Last week I introduced the songs and we started working on them. One of the songs I didn't know too well, and I taught a few pitches wrong. Now those are stuck in their heads, and when I worked with them this morning, they have the wrong pitches in their minds. So, I am trying to get them to sing the right pitches (which are actually easier), but I don't think it will happen. They can sing them in isolation, but not within the context of the song. Well, if they miss those pitches (which happen twice), no one will really know but me.