The prarent of middle class family son.

I think that every parent wants their child to have the best, and fruition into decent human being. Your parents manifested the lifestyle through hard work - meaning that this is the life they created/wanted. If you take advantage of your parents then that would call for ill feelings but this doesn't seem to be the case. When you get older, and pursue your life, as your parents had done, I believe you'll look back and understand.

Is there anything else in particular that you feel guilty about? You stated all the things they have given to you?
Like I mentioned before, you were born into the family you have. Take every opportunity that your parents provide. You never know what will happen in life, maybe your parents both lose their jobs, or one becomes ill, and etc. If I had a child, I would always want the best for them because in life, there are no guarentees.

On a side note, people are unique. Some people will not have to study hard for tests while others do. It's just who we are. Concern yourself with your own success and strive to do and be the best you can.