Do you beleive this to be a bit excessive for a 2nd grader?

My stepson is 7, & today he brought home some homework that consisted of him seeing how much his spelling words were "worth" He has 20 words,each word five to six letters, and if a=1, b=2, etc. , he had to add up all the letters & come out with the answer. He could not grasp the idea, even after I made hima chart of the letters & what number they correspond to. It took us an HOUR to get this done. He has homework every other day, this week also including putting all the words in ABC order, and writing 20 sentances including each word. My 5 yr old is the same way. Once a week, he brings home a picture and has to write a short essay about it, being at least 4 sentances. They both already have a negative view of school, even though both are very smart. It just really frustrates me that they get only 20 min. of free play at school, the rest involves sitting down and doing work, plus they are expected to do homework. Anyone else see this as being a bit excessive for such small children?