One of the biggest differences between middle school and high school compared to the elementary level is the development of higher learning skills. At the elementary level, students give information back, put together ideas and do some trouble shooting. As students reach the higher levels of education, they are expected to trouble shoot more, make inferences and put together a much more intricate process of thinking skills in there answers to homework and tests. Students are expected to expand on their readings to form a much more indepth answer.
As a parent, it is critical to not only check your child's work, but have your child expand on the work. Ask your child to "teach" you what he/she is learning. By verbally explaining the material the student has a much higher retention rate of the information. Statistically, a student who listens to someone teach, retains 10% of the information. If the student can teach someone else, retention of the material rises to 90%.
If you do not feel equiped to do this, a good tutoring program can set you and your child in the right direction. Learning Tree Tutors, with its credentialed teachers, specializes in this form of education. This is why LTT has had such a high success rate in the last 26 years in business.