The more reading children do, the more quickly they will develop as readers. It is often recommended that beginning readers spend 15 or 20 minutes reading each day (in addition to the reading they do at school. However, the amount of reading a child does is most important, not the amount of time she spends doing it. So, if a child spends 20minutes reading a book that is very challenging, she will read less (in terms of the total number of words read) than if she spends the same 20 minutes reading easier books.

While 15 to 20 minutes is the recommended amount of reading, it is important to

note that, if your child is interested in and enjoying what she is reading, it is fine

to encourage more time. However, we do not want children to become too tired.

Note that beginning readers generally benefit from reading to someone and many will not be interested in reading alone. Finding time to listen to your child read every day is important. Also, especially at the early stages of learning to read, reading will take

energy and concentration. Therefore, it will be helpful to find a time when your child is not too tired and a place where she can read without too many distractions (such as the TV or other conversations) going on in the background.

Reference

https://isaprofessionaldevelopment.org/documents/parent-booklet/PB-Q12.pdf