When you get to know Python, you don't need to "move into" Ruby or (shudder) PHP. It's much easier to learn a web programming framework in Python and how to deploy it, rather than to learn how your second programming language differs from Python.
The sad state of client-side programming is that you need to learn a lot about the messy world of HTML, CSS and JavaScript. Come to think of it, CoffeeScript might be a good language to start with today?
shrug
In my experience PHP or Ruby is generally a better/easier web programming experience (I tried Python but it never really clicked with the kids).
Python is a good general purpose language though.
The latter ones because you can start to get them to deploy/work on websites. Being able to write websites is a generally useful skill nowadays (even if you don't go into programming.. all my family need/want websites, for example).
I teach an after school IT club and a project to maintain/develop a site on the school intranet has consistently been the favourite :) Because it's something functional and visible!
(and also a good opportunity to teach about security issues what with the trial-by-fire environment a school brings :D)
EDIT: the other good thing about web-dev is that it needs a few different skills - design, back-end coding, infrastructure/sysops and databases which a) gives them a taster of all the career opportunities and b) lets different people "shine" in different areas, and contribute their strongest skill to the final project.