One thing I watch with great sorrow is how some religious, usually Christian, homeschoolers and curriculum publishers consider it necessary to obsessively dwell on one of the many interpretations of Genesis 1, particularly the meaning of "day" as used therein. The Hebrew word for day, "yom", can be used to mean an indefinite period of time, just as our English "day" can. Why is it necessary to rigidly require that it mean exactly the period that it now takes our earth to rotate one time? And why is it necessary to tie that rigidity to faith in the gospel of Jesus Christ?
First, the actual text of Genesis 1 makes it very questionable that a "day" of creation, as used therein, is a rotation of the earth taking 24 hours. It clearly states that the lights of the firmament (i.e., sun, moon, stars) weren't even in place and defining the days and years until the "fourth day" of the creation.
Second, the word "yom", as has already been set forth by others, is used to mean several different lengths of time in the Old Testament, including an age or even eternity. There is not just one possible interpretation of "day" in Genesis 1.
Third, faith in Jesus Christ rests on belief in his divinity and his power to redeem mankind. It doesn't rest on the Bible being a science text, which the Bible never claims to be. Faith certainly doesn't require that we dismiss as evil conspiracies the honestly inquiring minds of men and women with the objective, replicable results they have discovered just because those results fail to line up perfectly with our interpretation of the Bible. There's enough real evil in the world to deal with; we don't need to be turning scientists into bogeymen.
Fourth, the body of scientific knowledge grows as people pursue scientific knowledge, and so does the body of spiritual knowledge also grow, if we are willing to accept it. For example, when Jesus tried to tell his apostles--some of whom were apparently loathe to accept it--that his Messianic mission involved his imminent physical death, that went against their understanding and hope of what the Messiah was to be, yet with Jesus' resurrection his apostles came to understand that Jesus was accomplishing a far more important work than they had anticipated. We humans don't know all of God's ways.
Fifth, what are children to do who have grown up on a diet of math, spelling, reading, grammar, and sort-of science textbooks that dogmatically tie every good principle they're teaching to a literal 144-hour creation and young earth? When they grow up and find out that there are several ways of dating objects that show the world to be much older then they've been told, will they feel like they have to choose between Christian faith and the demonstrable marvels of modern science? Why make it so hard for them to embrace truth, be it revealed by God or man, for the sake of one interpretation of "day"?