Some teachers are clearly better at teaching than others. But it's more important to know that some teachers are a better fit for your particular child than others. For example, a strict disciplinarian is great if your child doesn't need much disciplining anyway, because noise and chaos from other students will be minimized, but for another child that teacher might turn the classroom into a battlefield and poison the joy of learning. So you want to learn which teacher is the best fit, not which teacher is the best.
This turns out to be a good thing, because it means that the people settling the classes can please everyone, instead of just the fraction of parents who want Mrs X because they've heard she's the best. It does mean more work for the class-settlers (typically the principal) and possibly the parents.
What should you do? First, gather information. This is hard to do when your child doesn't attend the school yet, but simpler once you're there. Come to every parent-teacher night, volunteer appreciation barbeque, concert, sports event, fundraising bake sale etc etc. If you can, volunteer at the school (milk lady, headlice checker, reading to the Grade 1s, whatever your school wants of the parents.) And when you're there, surrounded by other parents, talk to them. Many have a child older than yours and can tell you about the teachers - their styles, their strengths and weaknesses, etc. You will probably also get a chance to see the teachers in action, even if it's just watching them on yard duty or in the hallways. Field trips really show a teacher's personality as well. If you can, join non-school activities like skating, scouts, gymnastics etc that pull kids from the area - those parents who are watching along with you (or volunteering along with you) probably know the teachers too. Talk to every parent you can.
Second, once you know that Mrs X would be a great fit for your kid do not contact the school and ask for Mrs X to be your kid's teacher. If you feel that Mrs Y would be terrible, do not ask for "anyone except Mrs Y." Instead, do three things:
- list out to yourself what you think is vital for your kid to have a great year. The kind of teacher it is, whether their best friend X is in the classroom, being a split class (eg Grade 2/3 in the same room) or not being one, you liking the teacher (my kids loved teachers I hated and vice versa) and so on
- decide what the top two or three things are
- write a letter explaining about those things and asking them to be taken into account when settling the classes
Why not just say "I want Mrs X" or "I don't want Mrs Y" ? Because the principal can then tut to themselves about how naïve parents are and they don't know all the stuff the poor overworked principal has to take into account when mixing classrooms. Which is true: you don't want all the kids with involved caring parents in one class; who will volunteer in the others? You don't want all the rambunctious loud kids in one class, or all the timid and shy ones either - it needs to be mixed up on a lot of axes. So you are not telling the principal what to choose. You're providing some information that might not otherwise be available, about your child fitting well with a strong disciplinarian or a soft soothing type, or an outdoorsy nature focused type. But you're doing so know that there is only one "outdoorsy nature focused" teacher in your child's grade, and that you like everything else about that teacher and want that teacher for your child.
Everyone I know who does this has got the teacher they wanted every time. Ten or more years in a row per kid. But one more thing: nothing will help your child in school more than you being involved in the school. Coming on field trips, coming to events, knowing the teachers and the other kids by name and them knowing you. Your kid will get the benefit of the doubt in a lot of circumstances if the adults involved all feel good about you. Your letter asking for something is more likely to succeed. And you will know what is happening and what the issues are if things start to go badly for your child. Be there as much as you can.