Nat really varies with her sleep. Sometimes she is awake until quite late (9ish or *gulp*, later). In bed, but still awake. However the following night she will likely be asleep by 8. She tends to wake about 6:45/7am. And some days she does a catch-up sleep where she will have maybe 11-12 hours in one night (if she doesn't wet the bed, that is :/).
I think Lil's probably just really tired from the new routine. Nat went through it too, and last week was the same again. She was really tired, regardless of how much sleep she was getting. 10 hours sounds reasonable to me (if it's solid & not broken), with a longer night here and there to catch up. Hope she is enjoying school