DrRacket: No signature (blue) boxes for teaching languages?

[Kennis Koldewyn]

I'm running DrRacket 7.5 on MacOS 10.14 (Mojave), and I'm seeing the "signature boxes" (previously known as "blue boxes") as expected in the upper-right corner of the definitions window and the interactions window when using the Racket language.  However, if I choose a teaching language (Beginning Student, Intermediate Student with lambda, etc.), then the signature boxes are never visible, even though the checkbox "Show signature boxes and signature box arrow semi-circle in upper-right corner" is checked in the preferences.  Is this by design, and if so, is there a way to change it?  I'd like to introduce a young student to Racket, and the signature boxes would be very helpful (since it basically brings a big chunk of the documentation right into the user interface).

Best regards and a happy new year to all,

Kennis