1. Very few Chederim (elementary schools) teach any Tanach other than Humash and the first few historical books. These books have been “best sellers” among Yidden for the last few millennia. Siddur and Talmud are okay, but if you tried teaching them to little kids it would bore them to death. Much of the rest of Tanach (with a few exceptions, such as Megillas Esther and Yonah) would not go well with kids learning to read.
2. The goyim’s “Bible” is an adaptation based on several intermediate translations of dubious accuracy, and in many ways reflecting Hellenic culture. Yidden learn the original with Rashi, which gives an entirely different result. It is not surprising the goyim are easily confused (from out perspective, they are functional illiterates). A good way to shut them up is to make it clear you have never heard of “Genesis” or “Psalms” or “Moses” or “Isaac”, and after they explain remind them what the real names are (note that the number of goyim with even cheder-leval literacy in Hebrew is negligible).