In Dallas ISD for example, until about two years ago, they used *three* different sets of software for enrollment, attendance, and grades - even though EACH of those software suites were capable of managing all of it on their own. But since someone knew a guy who knew a guy, the district tech folks signed contracts, and a cluster**** was born.
Best part: when they transitioned away from that system, they simply implemented the new one and deactivated the old. In the middle of summer school - with no training for teachers, counselors, or administrators, let alone district level folks. Have fun putting in your grades, everyone!