Learning how to read from an early age is very important as it will set you up for the rest of your life. Being able to read is a necessity in your everyday life, whether it is reading a restaurant menu to looking at a simple message in a birthday card, there is not a day that goes by where you do not have to interpret something of some sort.
In key stage 1 of school it consists of children between the ages of 5 and 7 and they are taught comprehension in a class of roughly 20. You may think that a full lesson in this subject seems bizarre as it must be difficult to keep a full class of very young children engaged just sat still listening to you read book after book to them or even having them read to themselves, but there are a variety of different ways of learning how to go through text than just by looking at books.
Think how many things you read a day and in many different places, most of which I would guarantee are not in a book. Teachers use many different techniques to teach the children and use a variety of medium. If you just keep teaching one form of learning repetitively you are unlikely to progress as well. You begin to lose interest quickly, especially at a very young age as their minds need to keep being challenged to keep their focus.
They will also keep being challenged by learning more difficult words the older they become and the number of pages in books they read will start to get longer to make sure they can hold the interest of reading for longer. The teachers can test the children in a number of ways to make sure they understand what they have read. They can give out a word to each child in the class and get them to write out the word and decorate it however they want; using stencils, drawing pretty letters etc. then get the class to stick their words up onto a display board and check each others are correct. The teacher could then test further by swapping the words around.
Writing pieces down in a fun and creative way will help make learning easier and more appealing to some children and using visual aids such as pictures and displaying their own work up onto display boards can make children conscious to get things right and make sure that they take in the information.