Preschoolers are not too young to learn about reading and writing. In fact, exposing preschoolers to letters, words, rhymes, storybooks and other literature can significantly improve their reading and writing abilities later in life. Give your preschoolers pages with letters to copy or write on dotted lines, or have them construct letters with modeling clay. Ask your preschoolers to match a word on an index card to a picture on another card. Lay out a set of cards with letters and have the children spell their names. Say a nursery rhyme and have the kids clap the number of syllables as they repeat it. Have your preschoolers look up words in the dictionary that begin with the same letter as their own name, then have them try to create a sentence with the word.
Math doesn't have to be boring, especially if you make it fun from the beginning. Place some index cards with numbers on them in front of groups of objects of the same number, then say a number and ask the children to identify the proper group. Mix the numbers up and have the children match the numbers to the right group. Draw numerals with dots and have the preschoolers connect the dots to gain experience writing the numerals. Give your children a number, like "5," and ask what formula could give you that number -- i.e. what numbers you can add or subtract to get "5." Make a big clock out of colored paper with movable hands and have your preschoolers move the hands to the time you tell them. At home, take your preschooler to the store and ask her to help you find the best bargains.
Preschool is an excellent time to introduce science concepts. Children naturally wonder how the world around them works. If you feed their curiosity while instilling rigorous methodology, they will be well-prepared for both science classes and critical thinking. Have preschoolers grow vegetables like garlic, carrots, beets or avocados, which can be grown from the roots or seed found at the grocery store. Put white flowers in different-colored water and let them watch the flowers change color. Talk to them about how plants grow and how important they are for people. Take your preschooler outside to watch clouds shift, let them look through a telescope at distant stars, have them look through a microscope and watch ants under a magnifying glass. Inspire them to contemplate the vastness of the universe and the smallness of the microscopic world around us. Show them a tornado in two, conjoined, two-liter bottles to talk about the weather; have them pick up litter around the school or their house (with adult supervision) to address the topic of environmentalism; have them examine different rocks to illustrate the composition of the Earth; and show them what happens when you mix baking soda with an acid to demonstrate the importance of science safety.
Preschool education is not simply about learning to read and count; it is also about learning to get along with other students and take responsibility for oneself. Encourage your preschoolers to express their emotions in a healthy way by having them draw pictures of things that make them angry, sad and scared, and talk about ways to handle those circumstances. Tell them to pretend that a certain situation has happened to them -- like a classmate took their crayon -- and ask them how they would handle the situation. Let them write a list of things they love and have them share one of those things with someone they don't like. Expose them to different cultures by bringing ethnic snacks to the classroom (or cooking them at home) and talking about where that cuisine originates. Have your preschoolers spin a globe and point to a location, then draw pictures about the selected place. Teach your preschoolers to enjoy chores by turning them into a race or a game.