check-expect errors/failures should cause messages

[ccshan]

How can we provide negative feedback to a student who submits code such as the following in the Beginning Student Language?

(check-expect (+ true false) 123)
(check-expect (+ 1 2) 4)

(require 2htdp/image)
(require 2htdp/universe)
(check-expect (key-event? ke " ") " ")

Thanks!