I do not believe children should learn to read by purely memorizing words.
It seems inevitable that children will come across a word they do not know and will have no tools to figure out that word. I feel that children need to know their Letter Sounds and Grammar rules so that they can decode unfamiliar words.
However, there are words that children should memorize. These words are called, Sight words. These are the most common words children will come across when reading. In order to improve reading comprehension Sight words should be memorized.
Nevertheless, I do not believe children should read by trying to memorize every word.