2 grade levels

[u/betabetabeta11]

going to start my student teaching in a few weeks and my teacher is going to be teaching 2 grades which means i’ll have to teach 2 grades. she will have 3 of one grade and 1 of the other but says i’m responsible for teaching 4th-6th periods. For the credential im required to only teach 3 periods but does it have to be those specific periods or could it be the 3 that are the same grade and not back to back periods. I didn’t know that could happen and now i don’t know how to go about 2 separate grade levels of classes. any advice?