Parents are most often the best judges of their children's capabilities, but sometimes they underestimate what their children can do, say Dr. Richard Rubin and John J. Fisher, coauthors of ''Your Preschooler'' (New York: Macmillan, $10. 95). In their book, they offer ideas for a variety of household chores young children can learn to do or at least help with.
Cleaning up. One of the first things children learn is to pick up after themselves. According to Mr. Fisher, physical order becomes very important to toddlers as they begin to define their possessions and where they belong. By age three, children can often do cleanup themselves with minimal prodding and encouragement from parents.
The authors suggest letting a child join the parent in thoroughly cleaning a room. A preschooler can mop and sweep if he has a child-size mop and broom. Polishing furniture, the authors say, is especially enjoyable for young children. And once a job is completed, it's always important to give credit where credit is due.
Laundry. The first job children can learn here is to pick up after themselves , by putting their dirty clothes in the hamper. Children might also enjoy helping a parent load or unload the washer and dryer, helping to smooth and sort clean clothes, and put them in the proper drawers.
Mealtimes. Toddlers can begin to help in this area by clearing their own plate and cup. They can help with other dishes as they become better at it. Preschoolers can easily learn to throw away paper napkins and sponge off the table after dinner.
Setting the table takes a little more skill. The easiest jobs are placing napkins and silverware at each family member's place. The authors suggest drawing a diagram of a correct table setting for the child to refer to while setting the table.
Preschoolers can start learning to do dishes with pots, pans, plastic mixing bowls, and other unbreakables. The authors suggest putting the child on a sturdy chair with newspapers underneath while the youngster plays in the suds.
Food preparation is another area where children can help. The earliest tasks to teach include spreading butter or jam on a slice of bread with a dull knife and carefully pouring liquid into a glass. When parents have the time, the authors suggest letting the toddler help measure ingredients, grate cheese, sift flour, or take over stirring when the parent's arm gets tired.
Baby care. Toddlers are often asked to do a lot of fetching and carrying for their new brothers or sisters. Some children are quick to learn how to comfort and entertain the baby, whereas others can be less than gentle. Consider the preschooler as only an assistantm for baby care, the authors emphasize.
Yard and garden work. Some outdoor jobs for preschoolers include teaching them what weeds look like and how to pull them. Young children can also help plant flowers in spring, and may have fun picking the blooms later and helping to arrange them for bouquets in the house. In the fall, children equipped with child-size rakes can help gather leaves into piles that are great for jumping in and making tunnels.