Here's a link to a folksong and some images of the Chinese in the history of the railroad:
If I were teaching fourth grade, I would include this as part of the story of immigration in California or as part of the building of the railroad.
It is performed by a California folk band called The Black Irish Band. I looked and looked for the lyrics online, but they don't seem to be there.
BTW, it's worth it for fourth grade teachers to download their entire album "California Story". IMHO the singing and lyrics are a tad amateurish, but I think children would enjoy it and teachers would find valuable its ballad of John Muir, the tale of the last California grizzly bear (shot in 1922)--but have a box of tissues on hand, another tale of the building of the railroad but from an Irish view, plus a very John Denver-like song about the Sierra, and more.