I have taught the 17 year old class, the 3 year old class, and am currently teaching the 6-7 year olds.
We never had any kind of preogress report, but I would call the parents and speak with them if needed.
In our church, if we have a hard time with the child, we get the parent. They either have to take the child, or stay with them for a time in order to regain control again.
I've only had to do this maybe once or twice, but my classes are easier to handle since they are 1 age group as opposed to a vast age range.
In the children's case you are watching, it sounds as though the parent's aren't much help anyways, so the behavior issue may start from a lack of follow through disipline at home.
To tactfully bring this up with the parents, you must remain objective about their behaviour... for instance, instead of saying "they act angry and frustrated"... say "they tend to yell at the children and throw themselves on the floor and wrestle during the lesson".
Say something to the effect of, "We are so glad your children have come to join our class. They have such wonderful qualities in _____ areas. Yet, they are having touble with some of these issues:______. I understand some children have a hard time adjusting to new teachers and classmates, so is there anything we can further do to make your children feel comfortable in our class?
As far as discipline goes, speak to your Sunday School coordinator, as they usually have rules for this. Trying a time-out redirecting their behaviour, or asking for another assistant may be neccessary.