Middle- and high-school students with experience (or very strong interest) in technical innovation are invited to apply for the L3 Innovation Challenge, an intensive program of classes by Youth CITIES focused on the convergence of engineering, computing, and life sciences for innovation in healthcare.  Selected students will meet in Cambridge from 5PM to 8PM on Wednesdays from October 7 through November 18 for guest speakers, mentoring, discussion, and prototyping.  These testimonials give a sense of the program.  The cost is $395 + $75, and financial aid is available as needed.  Apply online by September 21.  (The program description says the deadline is September 25, but the application says September 21, so be early to play it safe.)  Students will be selected based on quality of their applications and notified by October 1.