The problem is not about updates being infrequent, it's about updates being wrong or partially applied for days at a time.
If the official way to check grades is online (and it is, by school policy and pointed out in every teachers's take-home documentation and in the open house nights where you meet your child's teachers), then I would rank accuracy first with timeliness a distant second.
If the official way to check grades is online (and it is, by school policy and pointed out in every teachers's take-home documentation and in the open house nights where you meet your child's teachers), then I would rank accuracy first with timeliness a distant second.