“One of mine also did a trail building project as part of a camp program. No cultural exchange but lots of hard work including cutting small trees, moving rocks etc. (with fun built in). I am not sure it was different than the trip to Central America or the work he did locally with Habitat or the church homeless program.”
Posters need to read the NYT and HuffPo links, because many are still missing the main point. The trail-clearing kids were not displacing local skilled labor, which is what happens on some of these house building trips. An NGO or a church with a long-standing relationship in a country where they do their work would wisely use donated money to send skilled help and/or to hire local masons or carpenters to accomplish the same thing some of these HS kids do - for a fraction of a cost, with much better quality.
And from what I have heard, Habitat for Humanity will first check a volunteer’s skill level, then assign them to a project accordingly, so no unskilled high schoolers would build crooked walls. Houses built by HH in the US still have to be to code and pass inspections. If you have never used a hammer, you would be either taught how to use one, and if you still struggle or do not want to hammer nails, removal of construction debris and sweeping is a big part of the overall job.