I hear ya - some of the parents in my 1st grade religious-ed class bring the child to class, but skip Mass! We have class every Sunday between the two morning Masses. Not the child’s fault, but there are times when I would love to teach the parents in class instead!
That was my experience when I served as Director for Religious Education. One year, a new mother decided to sign up her 13 year old daughter for religious education. Asked about previous classes she had attended, the mother said "none". To compound matters, the child had been baptized in a hospital and made First Communion but not First Penance. Since this was a small parish, I felt the best approach was to work with the child, one on one, using the Baltimore Catechism. A few weeks into the program, another mother saw the catechism in a pew, picked it up and exclaimed she had never learned any of this and could I teach her!
You are absolutely right! The problem is less the children and more the parents who were never properly catechized in the first place. There are a wealth of programs now to educate parents but, unless they are done at a time convenient for the mother, it's nothing more than wheel spinning.
To counter this problem, I now use the weekly bulletin to educate everyone via a column on the Year of Faith.