It is amazing the difference in effort you will get from worksheet to worksheet. Granted the amount of effort may vary immensely from year to year depending on the group of students you have.
Even the youngest students--kindergarteners--will benefit from printable worksheets. They will help your little one learn and master basic concepts in way that will capture and hold their attention. Remember that small kids enjoy doing things rather than simply reading or listening.
When a child learns to relate math to everyday questions, he will be great at it from the simplest addition all the way to trigonometry. To convert percentages, decimals and fractions is thus one essential skill.
From a teacher's perspective our competition is tough. Passing out a handout of 30 problems that are all in a format of 534x25= is not as stimulating in the students' eyes as playing games such as Grand Theft Auto and Resident Evil.