This comment stream has deviated from anything useful to Raspberry Pi, so I'll just make one more recommendation for Gambas for Linux:
Raspberry Pi will run GNU/Linux; Gambas is free, open-source BASIC for Linux.
Gambas is a professional-grade programming language and has an excellent IDE. It enables OOP, classes, modules, and forms, and has a full set of components for scripting, arrays, database programming, network interfacing, etc.
Gambas does not need line numbers, GOSUBs, GOTOs, etc. -- in this way, the procedural code is very similar to QuickBasic. Gambas allows you the option to use them, however, and line numbers are handy for debugging.
Gambas directly integrates Qt, so that you can directly read and edit the parameters for those toolkits in a sidebar on the Gambas composition screen. This means that children (and everybody) can immediately drag and drop buttons, listboxes, pictureboxes and every other Qt object directly onto any forms that they are composing.
To download a free 365 page manual in PDF form, including project files in tar.gz format, go to this address: http://beginnersguidetogambas.com/
After you get the guide, go to the Gambas main page: http://gambas.sourceforge.net/...../main.html
I recommend reviewing what Gambas is, before judging that BASIC is not worth teaching to children.