On Facebook, it’s the season where parents are posting pictures of K-12 graduations, including moppets in tiny mortarboards. But unlike a generation ago, today’s smallest graduates are amassing a big data trail. Just as medical and government files have been digitized — some to be anonymized and sold; all susceptible to breaches — student data has entered the realm of the valuable and the vulnerable. Parents are paying attention. A recent study by the company The Learning Curve found that while 71 percent of parents believe technology has improved their child’s education, 79 percent were concerned about the privacy and security of their child’s data, and 75 percent worried about advertiser access to that data.