With many 1 1/2 story house plans, you'll find the master suite on the main level for maximum convenience and easier aging in place. This is becoming a popular layout choice. When the secondary bedrooms are upstairs, it also gives the master suite extra privacy, which can be welcome with school-age children.
Other plans with 1.5 stories may feature large lofts upstairs. Use these versatile spaces as home offices, libraries, homeschooling centers, craft spaces, or even art studios.