"I can not apply an assignment to all my classes even though they are the same class (ex. Meteorology) - why?"
(post repeated)
You are not seeing all your sections because you have
another teacher assigned to some of them. For example, an ESL teacher is
assigned to section 1, 3, and 5 so you might see all these sections grouped
together, but not the others.
At this time, Infinite Campus does not see this as a bug. We have no indication that it will be changed in the near future.
One solution is to remove the co-teachers from your sections so you can see all of them when entering your assignments. If ESL teachers or CC teachers need to see grade information, they can access the grades tab for each student.
If it's necessary to have the co-teacher, then after creating the assignment in one section, use the Copy assignments feature in Instruction->Assignments to copy to another section or sections.
Tina and Stacy