There was a time that the United States of America had some of the highest mathematic scores in the world for students in grades k through 12. A lot has changes since those days, and in order to help children get back on the path to being good mathematical students parents need to play an important role.
Sort it out! The sky is the limit when it comes to finding things to sort! Candy, beans, cotton balls, paper clips... you name it! You can even change around how you want it sorted... one time, sort by color, the next time sort by size or shape! My son had a BLAST when I pulled his Matchbox cars to the school table and we sorted them by color! For younger children, you can make it easier by having 'color cards' and have them match the specific objects to the correct card. Older children can just be told to sort out the items by color, shape, etc.
As children become more confident in their math skills, give them worksheets one grade level above their current grade. Help them if necessary, but when students become successful in the upper level workbooks; their confidence will really improve. The seed will be planted early and parents can watch as it grows.
The classes can be taught at the various colleges or universities in the local area. This is a community outreach for the colleges and universities, but children will develop social and academic skills that will carry over to their classroom and on to adulthood.