You're stressing too much. A still air bator can have a 3-4 degree difference between the top and bottom of an egg... a forced air can still have a degree or two difference between different areas. Your temps look fine. Rotate eggs around the bottom of the bator. If they hatch early, drop the thermostat down a half degree, if they hatch late, up it half a degree or so the next time. Every room and season will make a difference in how an individual incubator works. How the incubator works when you have eggs in it will also change! If you have eggs in there now, I'd not be fiddling with temps once you get it where you "want" or it will be hard to keep track of variables.
That said... a classroom hatch is ALWAYS a big gamble, even if you've hatched tons of chicks. Have back up chicks to bring in if the ones in class do not hatch. Heat off on weekends/nights, drafts, kids bumping into the bator or thermostat, janitors possibly unplugging it. Many things can happen in a classroom to cause a bad hatch. Add shipped eggs to that and you will want back up.
Good luck!
That said... a classroom hatch is ALWAYS a big gamble, even if you've hatched tons of chicks. Have back up chicks to bring in if the ones in class do not hatch. Heat off on weekends/nights, drafts, kids bumping into the bator or thermostat, janitors possibly unplugging it. Many things can happen in a classroom to cause a bad hatch. Add shipped eggs to that and you will want back up.
Good luck!
