You need a teaching certification, but studying the computer field is a good thing.
The problem with the IT field today is that it is just like the "car repair" industry. Everyone and his brother thinks they can fix cars. Same thing with computers. Everyone and her brother thinks they know computers....
In both industries, what they do not realize is that the things they know are really what a general user should know. If they can't build a computer from scratch (and I do not mean buying plug-in boards) they don't really know hardware.
If they can't write their own programs from scratch, they do not really know programming.
What do you want to be able to do or to teach? There are many different courses of study in this very broad field. In most schools & colleges, they will break these down into individual fields, so you will not study the entire computer field. You could study Computer Science (which deals with the hardware theory, computer architecture, applications, & systems building), but you specifically mentioned IT, and most people use this to refer to the software side of the business..
Some of the other answerers mentioned a few, but they forgot many other computer related fields. There are software design, algorithms (how to solve problems with computers), artificial intelligence, bioinformatics (and the medical field), security (very important, nowadays), 3D-modeling (important in design work) and animation (Not just important for the gaming industry, but in many others as well.).
The other answerers mentioned certifications, but for teaching those are minimally useful, -if at all. Schools and teaching jobs want to see actual degree experience that shows you understand the broad picture, not just that some company certified that you know how to fix a certain brand-name of router or operate some specific program. An MCSE or the lesser degrees like A+ are basically worthless in the education field. They are used in industry to show that someone without a regular degree at least has some minimum familiarity with the subject.
Here is something that may be of interest:
Expected total earnings over a 40-year working life
High school graduate: $1.2 million
Associate's degree: $1.6 million
Bachelor's degree: $2.1 million
Master's degree: $2.5 million
Professional degree: $4.4 million
Doctoral degree $3.4 million
Source: United States Census Bureau
My advice here is to talk with a councilor in the school you are thinking of attending. Find out what all they offer, how long it will take and at what cost. Mention to them that you wish to go into teaching and see what sort of degrees they offer that will include this.
I hope this answer helped.
______________________________________________________________________
To the one other answerer who said he had no degree and was making 90 grand a year, --Ha ha... Yeah, RIGHT! That's funny.
By the way, Derrick, idiot is spelled with one 'd', not two.
4.8% of employees in the (entire) technology field do not have any college degree, however, they are also on the lower paid end of the specturm, usually making less than $40,000 a year.
I worked in that industry a long time and only got to the high salary range after 20 plus years in the industry. You say you are 27? That means you have roughly twelve years left, to earn good money in the computer industry. True you can have several jobs lined up, but when you turn 30, they start to question whether to hire you, and at 40, you're out totally, unless you have a masters or a doctorate. As soon as you turn forty, most big companies will be looking to get rid of you, (for one thing they don't want to have to pay you any retirement and if they keep you too many years they are required to do so.) and if you are out of work, you won't find a job once you reach 40. Sad, but a fact of life in the IT industry. They don't talk about it, but it is a fact. Are there any CS people where you work over 40? Look around. When they get to the point where they are thinking they can retire in a year or two, that is when the company will let them go and hire younger people. You can read about the trends in the industry many places on the internet. Don't just take my word, --Check it out.
Here are a couple places you can read about it:
http://findarticles.com/p/articles/mi_m0EIN/is_1998_Sept_17/ai_53014536
http://www.mydd.com/story/2008/6/23/63424/5831
It is funny also that you referred to a couple old men in the other answers, when you only have a couple years till you get into the "questionable" range and 12-13 before you are an "old man" too. How old will your kids be when you reach 40? Are you providing for them when you are out of work? Alternatively, do you have another line of business? (And I am not thinking of McDonalds burger-flipper or WalMart greeter...) You still have time to get that degree –not for your current job, but to protect your family and your future, while you are making enough to pay for the schooling. (That's what I did. It was hard working days and going to school nights, but it pays off in the long run.)
You mentioned getting on the phone to interview and they don't ask you about your degrees. This is a no-brainer. Before you can interview, you had to send them a resume or CV and you would have mentioned a degree if you had one. You would have mentioned college if you went. So the only thing left that would get them to hire you is if you have sufficient certifications to show you may be able to do the job.
Generally, only teachers or government employees can keep working in a good job in IT/IS/CS when no longer a "kid", so whatever you are really making, make sure you have a 401k or some other investment strategy that will carry you.
The IT industry makes big money, but the companies like to keep it, rather than share it with their employees, and they know that older employees will demand higher wages. They can hire young guys for much less to do the job. Only the business owners and board members are making the big money.
I didn't become a millionaire until I got out of the computer business and started on a different career. (I have doctorates in three different fields.) If you don't have at *least* a BS/BA degree and really are making decent money, you were as lucky as someone who hit the lottery. Enjoy it while you can. Good luck.