XHTML 1.0: The Extensible HyperText Markup Language (Second Edition)
Unless I'm reading that backwards, it says to include the space. It's not necessarily required, but it is recommended.C.2. Empty Elements
Include a space before the trailing / and > of empty elements, e.g. <br />, <hr /> and <img src="karen.jpg" alt="Karen" />. Also, use the minimized tag syntax for empty elements, e.g. <br />, as the alternative syntax <br></br> allowed by XML gives uncertain results in many existing user agents.
Also, what do you wish you could believe? That I have taught and done (and am still involved in at a different level) curriculum development?
I agree that you should challenge a student. However, there is a difference between giving a kindergartener a Calculus III problem and giving a college student a critical thinking problem. You can't challenge a student if they have no information yet. Let them grasp the simple basics first, then push that information and their knowledge further with challenges. Giving a student a challenge they are prepared for and trying to give them a BS in Computer Science worth of information on day 1 are two very different things.
I've never thought a student too dumb to do what is required and I would frequently challenge my students to solve problems that I never directly taught, but that they had the ground work for... requiring them to think outside of the box.