This teacher should believe in giving homework every night. Homework reinforces what was taught and learned in class and gives the parent and the teacher a chance to see if the child understands that information.
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.
For example, all children should learn their multiplication tables by the third grade. They should be able to repeat them, verbally, without using a calculator. Children in elementary school who rely on the calculator for the answers are creating math deficiencies, which could have a negative impact on their math development.
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.