A thought from a parish-level teacher:
The teachers we get in Catholic Schools are professional teachers. But the teachers we have in parish CCD/PSR classrooms are not. The days of having nuns in the classrooms are nearly gone.
We are volunteers. We are not professionally trained. We are not theologians, and only a portion of us have studied religion in college. We make every serious effort to know our material and present it correctly anyway. But we are not beyond making mistakes in fact, interpretation, or presentation.
If you hear your child telling you something his teacher said about the Church or Catholic Doctrine, which contradicts what you know, by all means say something to the teacher.
Please be charitable and first ask whether your child understood it correctly. Your little one may have been distracted and not paying attention, or didn’t know the meaning of the words and thought the teacher said something else.
Also, please take the time to look up the issue yourself. It’s entirely possible that something you knew for all these years was actually incorrect.
Show your child the correct teaching in the Holy Bible, and also in the Catechism of the Catholic Church. If you don’t have a copy of the Catechism in your home - Get One. The pocket-size edition has a complete topical concordance in the back, costs less than $10.00, and is available at any bookstore. It is the best $10.00 you will ever spend. (I prefer the big volume because it has more appendices and is easier to flip through / read; that one still is less than $20.00)
Finally, please, please do bring your concern to the teacher, and bring your bible and catechism with you. We will both learn something, and will both be better prepared to teach your child and all the rest of God’s precious children.
Thank you.