My secondborn, now 5, will be starting school next January. Both she and her almost-7-year-old sister (who's in her second year of school) are getting very excited about that fact. The girls, while they have their share of sibling moments, are very close, and they miss each other when A, the eldest, is away for 6 hours a day at school. They are already plotting the games they'll play and the fun they'll have sharing recess and lunchtimes, and A is vowing to take care of E (the younger one) "ALL the time!"
As part of this school-preparation excitement, this week, A and E have started playing schools at home. A, who is convinced that her little sister is brilliant and perfectly capable of learning all the same things she is learning, has been spending patient hours sitting with E and their maths cards, going through times tables; reading to her sister, and getting E to read words back to her; and teaching her school protocols (they insisted on having their sandwiches on the weekend in school lunchboxes and timed their eating to the length of the lunch session at school!)
This is play that they have initiated themselves and involves both role-playing / norming behavioural play as well as keying into core interests for them both. A is loving the opportunity to teach what she knows to E, and is doing so with remarkable gentleness for a child her age. E is basking in her big sister's encouragement and between A's sessions and the phonics she & I work on together most days, she's reading (albeit haltingly) now.
I think it is great for kids to be able to recast their daily experiences through play and to be able to reinforce what they are learning by passing it on. It is benefiting them both, this schooly play.