A parent must know what level of math and any other subject, for that matter, that their child is performing at every school year. When children enter kindergarten and the school recommends that children know their ABC's and know how to count to twenty or whatever number, it is the parent's responsibility to make sure the child is prepared prior to enrolling in school.
I have observed teachers who really challenge their students to achieve higher order thinking These teachers take their students as early as the Second Grade and teach them how to add, subtract, multiply and divide using only their bran. We call this Mental Math. When I observed a Second Grade Class that had their students mentally answering math computation questions, I put my own son in that class. Shortly after being enrolled, He, too, learned how to do Mental Math. From that point on, math was my son's best subject. Teachers can really make a difference and parents can help affect change.
The addition, subtraction & number counting worksheets are meant for improving & developing the IQ skills of the kids, while English comprehension & grammar worksheets are provided to skill students at constructing error free sentences.
The same general idea worked when it came to my son's Lego's! It was a great way to work on patterns and following directions! I would draw a pattern on paper for him to copy and recreate with his Legos. It not only helped with his color recognition, but his problem solving skills, fine motor skills and he didn't even know he was doing math!!