I took 2 years of technical school (a technologist diploma), and then went right back to repairing consumer TV's like I was in high school at the local TV shop. That was in 1981.
Then in 1985 the bottom dropped out of the consumer TV market due to RCA, and I got employed by a night club installation company. There's nothing like a raging hormonal 24 year old that was sent to a strip club to (ahem) 'tune' up the sound system again, and again, and again... but I digress..
When Zenith came out with the first CRT projectro in 1985, I took my TV knowledge to task, and started selling, installing and repairing these sets. I sold about 60 a year, and serviced the ones that the competition sold but couldn't service.
Then when the company went under in 1988, I started out on my own... but enough about me...
If it's strictly installations that you're going after, forget the schooling and get right into being an apprentice at a high end A/V company. There's more of a physical art in installing an inwall speaker that isn't cockeyed than being an electronics wiz.
And frankly, a lot of the sales stuff isn't based on electronics, but on hocus pocus, and a seamless sales pitch (sorry guys, but it's the truth!)
Where the electronics knowledge and theory is mandatory is in service work. I've seen a bunch of installers install an entire sound system, but they can't repair it when something fails after they install it.
Problem is, unless you find a niche like me that can do board level repairs on CRT projectors, there's no money in service, trust me. For the most part, you pull out a bad component and sell the customer a new one.
I've got an ad running for an installer right now in the local papers. I'll probably get someone like an alarm tech that is unemployed and has good installation and customer service skills over someone that's a geek like me. Decent alarm guys have the skills to fish wires like nobody's business, and can doa neat job of it.
Sure, there's lots of facets that I haven't covered, like the programming, say of a Crestron or AMX unit, that's a whole 'nother ball park. And good programmers are worth their weight in gold....
Just my $.02.