Several events wont be unlocked until you have a high enough school level. May need high number of participants to unlock the Items. Summer Event is on 6th month and Autum Event is on11th month each year. Prompted at the end of 1st week and executed at the end of 4th weak of that month.

Item	How to unlock
Boat	Do Field Trip Event (Summer).
Camera Set	Do Field Study Event (Summer).
Dust Cloth	Build a Locker Room.
Fishing Set	Do Park Stroll Event (Summer).
Skate	Do School Trip Event (Autum).
Skateboard	Do Athletic Meet Event (Autum).
Sketching Set	Do Art Festival Event (Autum).
Ski	Do Ski School Event (Autum).