I'm preaching to the 4-digit choir here, I know. Let me issue the disclaimer that I am not a teacher but a bunch of my friends are, and my job does depend on staying up to date.
You're right, the gap cannot be mitigated. It's how kids' lives and brains work. We were the same way at one point, too. You'll never have as much time to learn new stuff, nor the same neuroplasticity, as you did when you were a bored junior high schooler with all those summers and weekends and snow days and such. It was nice to be so free from responsibility that I could drop a whole week's evenings into writing a DOS game in BASIC or C or assembler, or whatever else, learning while I did it.
Staying ahead of the kids requires a LOT of effort and an independent adult with all of the relevant things to take care of might not be able to stay ahead of the most dedicated ones. You may have the wisdom and specialization of years of experience (I'd like to see those kids build a robust enterprise network, or spec out an IVR soup-to-nuts) but being up to speed on all of the new stuff? Forget it. Grading assignments and planning lessons around an existing curriculum takes a lot of time and you just want a break when you're finally done at 10pm. You have time for some of the new stuff but not all of it.
I do think there should be in-service days, decent salaries, ongoing education benefits, etc for computer teachers. Attract some real talent.
After all: The new hires we work with today were those kids in a computer class just a couple years ago, so maybe schools can make better coworkers for the rest of us.