Beta in June, just in time for most schools in North America to be let out. I guess ready for the fall, assuming you have beta testers in teachers willing to work over the summer.
But with the iPad still costing schools the price of two Chromebooks, don't see Apple gaining much ground just becuase of a couple apps and pencil support.
Value of a $250 Chromebook after three years = $0 Value of a $299 iPad after four years = $50