For courses on the Lego EV3 robot, follow THIS LINK.
Here's a course that will help you build a robot powered by the Raspberry Pi and HERE is the accompanying text.
Robotics courses for teens include
See also this list of online robotics courses from Lego Engineering.
Khan Academy has designed a robot that can be built for less than 10 Euros and built by 8 year olds!
Some very advanced (undergraduate) robotics courses are available online free: