This may help.
To address comprehension... we must understand what is comprehension.
Comprehension is pretty much is to test how much the student understands the passage and able to express in her/his own words while answering the questions being set for him/her.
Hence to help your child... best to go through short passagew with your child and start to ask questions and your child along to answer them precisely and concisely.
Teach your child to understand the passage by bite size meaning... understand the passage paragraph by paragraph.
Why in the first place the passage is in paragraphs? As we know.. typically, you will have an introduction.. and following that another 2-3 paragraphs to build the story/contents and end with a concluding paragraph.
The other thing to note is that the questions are being set in top-down fashion, being the answers are found in top-down fashion from the passage.
Probably only in Upper Primary that they may ask the student to summarise how one's feel /learn from the passage.
As for composition... again, typically, you will have your intro para then couple of ideas to share to build up the story and content and a concluding paragraph.
Not to frighten the child... start with simple topic .. something that they can relate to easily like their favourite pet, their family.. so that you can share with ease... and encourage to write.
Construction of sentences and grammar, making the story interesting.. good vocabulary... this comes with practice and also, to read extensively.
dont't just read one type of books.... open them up to fiction and non-fiction books... even magazines... this will enlarge their scope... increase knowledge.. make them more interesting... and this will help alot in writing as well as other subjects.
The gift of reading... is the greatest gift parents could give to their children!
With the love of reading.. they can explore.. discover.. learn... and express themselves well. Regardless in school... in their day-to-day communications...and their life as they migrate to adulthood - family and career.
Hope this helps....