L.R.
You mention first thing in the post that it's a trend in your office. That is a red flag, to me.
Are you -- not your kids, YOU and spouse if there's one in the picture -- interested, excited, etc.? If this is driven by your kids and especially if there is some unspoken and unacknowledged pressure in the office to "do this great thing that the rest of us are doing" -- then do not do this!
Have you asked your coworkers for frank and realistic discussions about how this is working for them? Or do they just paint it all as fabulous every day? Do these hosting coworkers have kids the ages and stages of your own kids, or are they without kids? Are your own kids high school age (the age of exchange students) or younger? Each age would have its own issues with another person in the house for nine months. And if every single coworker says every single student is just perfect every day -- again, red flag that they aren't being realistic. Even the very best, nicest kid is going to have off days, or unwittingly cause some friction in the home when the host kids get tired of the deal. Are the coworkers admitting to that or does there seem to be some competition to appear to be having an ideal experience with this?
Your kids have only met the exchange students once, at a picnic, having fun and BEING fun to be around. Your kids have not thought through living with another person in their household 24/7; sharing rides, bathrooms, TV time, all meals, your attention, and everything else with a new person. Your kids have no idea of the commitment involved. So honestly, you can't let yourself be swayed by their one-time meeting with some fun high schoolers.
That's why hosting for a summer is the best idea here if you are interested -- so the kids and you get a more realistic idea of things. And even then, it's not fully realistic because a summer exchange student won't be around while your own kids are stressing about schoolwork, or want you to do something with just them, or are expecting to be driven to an activity and you're late because the student has to be somewhere too....
I would look for a summer exchange or a one-semester exchange. Not year-long. Yes, it can be great, but I see some red flags in your post: The fact it's the "thing to do" in your office and the fact your kids are so very enthusiastic based on so little.
I am not against exchanges! I was a summer exchange student to Japan years back and it was a fantastic experience, but it was made great partly by the fact that the organization that sent me did extensive preparation of kids for the new culture, how to act in that culture, what to expect, etc. This was just for a summer visit! If you do go through with this, go only with a reputable organization that does not want a ton of money from ANY party that's involved (there are fly-by-nights that do this just to make a buck), and be sure the student coming to you is getting advance training about what to expect in the U.S. I am all for student exchanges but it does introduce a new person into the family for a long time and can be hard to undo if it goes wrong -- so do the due diligence first, including asking yourself if possibly you feel some push to do this because your coworkers do it.