I agree with above posters that your ex is using son to manipulate you,
but I also think Lexie is right and that it is a good thing to learn to "deal"
with things like scheduling, classes, etc. since he will need to do that in college,
and later in his vocation.
Be a participant and take him to the school. Talk to the teachers and see
what they have to say. You might be surprised.
I am working with several public school teachers at the moment, and I have
been extremely impressed by their professional commitment to their students,
their pedagogical skills and strategies, and the quality of the education they strive to deliver on a daily basis.