A second grade teacher of a friend of my daughter taught her class that Columbus was not a nice man, and explained why. My daughter was not affected by this teaching. However, it brought up the question of what should I do when/if this happens to my daughter? Whether or not Columbus was a nice man, second grade is not the time to teach this and therefore I disagree with the teacher. What should I do should this happen in a class my child is in?
Teach your children to think critically about what they are taught
This way it will matter less what they are taught at school. You can present your view at home, and they can make a logical decision on which they accept. Of course this has the downside (if you consider it a downside, I personally do not) that your child will also begin to question what you tell them. But you will not be there forever, and it is much more important that they learn how to interpret and evaluate information for themselves.
It sounds like your concern is about a teacher mixing opinion with the teaching material.
If the teacher is presenting an opinion you disagree with, then you can raise the issue with them directly. I would suggest starting off by saying whether or not your agree with their opinion is not the issue, but rather that you are concerned that the opinion expressed is not appropriate for the child's age, and that you would request that the teacher focus instead on the facts and a neutral, unbiased outlook. Using your example, you could point out that they don't need to portray Columbus as a hero, but merely avoid going out of their way to make him look like a villain.
While not quite the same as your scenario, the steps of documentation and escalation described in this blog may be helpful.
It's fine to disagree with a teacher. And even fine to bring it up with them.
But if you disagree with curriculum and facts, then that's a whole other issue and you have two options:
1) run for school board and try to push your agenda
2) pull your kids out of public school and find a school that adheres to your own belief system
This is a very important and critical topic. It questions the education philosophy. The topic is about the definition of a "teacher". Is the teacher a facilitator helping the students read a book? Or the teacher is an educated thinker providing students with deeper understanding of the world? How much freedom should a teacher has to convey knowledge to the students? Are there other people more qualified than the teacher to control what the teacher says? How do we qualify those people? who qualifies them?
I believe in the parent's right to manage the education of the child. However, I argue that it must be macro-managed rather than micro-managed. This is because the parent may not have the knowledge, expertise, the ability, or the time to define the details of what the child should learn. This task is better be given to the specialists. What a parent can do is determine the broader curriculum and teacher requirements.
The parent has the right to determine the cultural values the child is exposed to. This is achieved by selecting the society to live in, the people to interact with, and certainly the teachers. Once the teacher is accepted, we must give the teacher the freedom to convey his/her knowledge, experience, thoughts to the child. This provides the child with wholesome eduction. The teacher should not be stuttering of fear to say something that may not be acceptable. It is unrealistic to think that we can predefine everything for the teacher to say.
What if the "accepted" teacher's opinion on a specific topic conflicts with the parent, or the school administrator, or some government official? The answer to this questions depends on the culture and the political system. In a free democratic society, the teacher should have the freedom to teach. The teacher's reputation defines his/her market. The parents can compensate for those specifics by exposing the child to other opinions.
What we can enforce on the teacher is not to grade a student based on an opinion. If the student has a logically presented argument, the teacher must accept it. A qualified teacher should know the difference between facts and opinions.
Unfortunately, most current education systems do not allow parents the freedom of selecting teachers. This is what needs to be changed.