Hi @C Wilson
We have the same issue and I raised a ticket with the service desk. They have confirmed this is a bug whereby assignments set with an issue date in the future are appearing and they are being notified about. This is a huge issue for us as we are using Frog for all homework now and students are sometimes completing assignments/getting anxious about not understanding the homework, before the teacher has actually taught them the lesson!
Tom
THaines's post in Assignments - Appearing before Issue Date was marked as the answer