Most American colleges finish their year by Memorial Day, and start their new semester (usually a compressed summer term) immediately after. We have different school schedules.
Originally the holiday was to commemorate Union soldiers who died in the Civil War (meaning a third of the country was indifferent). Today is it largely an occasion for picnics, cook-outs, and sporting events – and of course shopping. Given that very few Americans have immeidate family who died in military service (unlike the 19th century when that was the norm -based on population size, Civil War deaths would be equivalent of the US losing 5-10 million people today), it is understandable that the holiday has lost most of its importance.