Below is a calendar of sorts. This information provides us with the actual skills a child should have by a certain time.
When a child is in Kindergarten they will learn basic alphabet knowledge in the first eighteen weeks. They will learn the names and sounds a letter makes. In the next nine weeks a child will learn how to use those letter sounds to read basic consonant - vowel - consonant (CVC) words. The last nine weeks of Kindergarten will be matching patterns or finding those rhyming word patterns.
When a child is in First Grade they will learn all about blending letters together, like st, cl, dr, and tr. They will also learn about digraphs, sh, ch, th, and ph in the first nine weeks. The second nine weeks will be learning about the r-controlled vowel, (RCV) ar, er, ir, or, and ur. The following nine weeks should be vowel - consonant - e (VCe) words, like cake, bike, bone, and cube as well as vowel teams (VT) like ai, oa, igh, and ew. The final nine weeks of First Grade should be about fluency and comprehension.
When a child is in Second Grade they will continue to work on fluency and comprehension as well as vocabulary and comprehension. It's here they learn to take all of that coding they did in Kindergarten and First Grade and put it together to read those multisyllabic words. They are also taught about prefixes and suffixes and how to decode the big words with ease.
These first three years set up children for success in academics and life. When children are not on grade level they can sense it and begin to struggle in their confidence and readers and learners.