There are also ways you can support both your child and their new teacher as they enter the new school year. One of the ways you can do this is by offering the teacher 'cheat sheets.'
If you know your child particularly struggles with transitioning from one subject to another you can offer the teacher a 'cheat sheet' on how to be successful in this. For example, occupy fidgety hands with a small responsibility or something they can hold whilst they are transitioning classrooms.
If you know your child is likely to tantrum at the beginning of the day and not want to go into the classroom, offer a cheat sheet to the teacher or teaching assistant on best ways to manage this.
Example, don't negotiate or try to calm them down. Stick with the plan of being in the classroom, and wait for them to calm down. Offer lots of praise when you see appropriate behaviour.