Elements of schoolhouse style have been popular for at least the last half decade, from the boys rooms of RH, to the best of minimalist farmhouses. Traditional trademarks include the iconic acorn shaped pendant, plenty of glossy shiplap, distressed wood furniture, and industrial metals. The trick to getting it right today is to pick and choose a few key pieces, and avoid going bananas so that your place doesn't end up looking like, er, a schoolhouse. Here's how to incorporate the style, and…