The best time to start tuition is today. Try and find out what your child is struggling with and help him/her out. Often, children experience some Common Learning Difficulties (CLDs), which should be sorted out as soon as possible. These CLDs include such things as counting numbers, differentiating numbers, adding and subtracting numbers, multiplying and dividing simple numbers, appreciating the relationships between some basic operations, etc.
Learning should be fun and there are ways you could make it an exciting activity. Get your child to use an abacus to add. Encourage your child to use tallies and tokens while counting and adding. It is common to see children counting with the fingers. And this is also good for their mental development. Make sure your child appreciates what the problem is all about (the concept) and how to solve it (the procedures). They are key to understanding and solving mathematical problems. You must start from an early stage to improve their language proficiency. Your child needs to appreciate the use of language in mathematics as well as how to interpret word problems.