To boldly go.

Excuse me if this may sounds harsh or uncharitable, but my experience with American elementary school teachers has led me to believe that many, if not most, elementary school teachers are generally rigid in their way of teaching (my way is the right way, there is no other way), and refuse to address nuance, perhaps from their own ignorance, their patronization of children, or both. While we absolutely need and should support high quality elementary school teachers, the assumption I've developed is that most elementary school teachers are highly juvenile themselves, and are there partially due to their own lack of executive functioning, considering that elementary school is more similar to a day care than an actual educational facility.

I recall talking to an elementary school teacher who insisted that the only way to comprehend whether a number was even was to determine if the least significant digit was 0 or 2 and I was met with hostility when I mentioned that while that may be easier for the child to understand within a base-10 world, if even the educator can't understand why an even number is more accurately described as a number which when divided by 2 has a remainder of 0 then I should be very concerned about the state of education.

Tell my 2nd grade teacher.

No. You seem very confident, but octopi is (grammatically) perfectly acceptable. The English word octopus is taken from the Latin (coined by Linnaeus) word octopus, which is of Greek origin. Greek loanwords in Latin were used very inconsistently, but many people on the internet seem to believe that it MUST be a third declension noun. However, Pliny treats the structurally identical polypus as second declension and uses the plural polypi (see https://www.perseus.tufts.edu/hopper/text?doc=Plin.+Nat.+9&f...).