People have to start from the ground, then first step, second, third and so on to reach their destination floor. Exactly the same way students have to start from Kindergarten, then grade one, grade two and three and so on to reach their math destination. Also, if some of the steps are broken in the staircase, it is still hard to reach the desired floor using those steps. Same way, if you are missing some of the basic concepts from elementary grades, math for you is still hard. Now, the kindergarten, first grade and second grade are like first couple of the steps of the stairs. You can learn this level of math easily, as you can jump enough to take yourself to second or third step of the stairs easily. As it is very hard to reach sixth or seventh step of a stairs by jumping from the ground, exactly the same way to learn grade five or higher grade math is very hard (or impossible) without having the good knowledge of the kindergarten to grade three or grade four math. Now, consider one person is jumping on the ground to reach the third floor of a building. Can this person make it? Never, if he is not Spiderman. For this person, to reach the third floor by jumping is impossible or very hard and finally he gave up saying that it was very hard to reach third floor.
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. However for the most part, when a worksheet is needed to help drill down a procedure, standard, or lesson, its effectiveness can and will vary. Therefore it is our job as the teacher to make sure that when we need to utilize a worksheet, we provide the students with one that is as inspiring as can be. Times are different these days. Kids are growing up in a world of microwaves, fast food chains, Nintendo, Wifi, iPads, along with a ton of other technical marvels. When I was growing up we didn't have home computers let alone PlayStation to entertain ourselves. Handheld camcorders were barely coming to the retail market by the time I was in 8th grade, but still a long ways away from the YouTube and Facebook arena we now see today. Times were extremely different back then and so was school.