How can I put two or more spaces in a row in my posts? How about non-breaking spaces?
Try changing the font to Courier, which is a mono-spaced font...
I'm not a teacher, so please consider any advice I give in that context.
Would it be possible to get the custom BB code [tab] or something like it, to create a larger space of a pre-set size? Actually, there are lots of formatting BB codes I think could be really useful on here, for things like tables and so on - I tried looking up which you have installed but http://www.usingenglish.com/forum/misc.php?do=bbcode seems to be a broken link.