Charter schools are a big and booming business–so much so that the Capital Roundtable hosted a day-long conference back in July : Private Equity Investing in For-Profit Education Companies. Writing for Forbes magazine, contributor Addison Wiggin notes many opportunities to invest in the lucrative charter school gravy train. According to Wiggin, “About the only thing charters do well is limit the influence of teachers’ unions. And fatten their investors’ portfolios.”