I don't have first-hand experience with all the sailing and power-boating schools in the area. But these are ones I know well and can recommend. I work with many of them. But I'm don't recommend them because I work for them. I work for them because they are the type of school I can personally recommend!
At the bottom of this page is a very complete list of sailing schools, updated annually by 48 North.
American Sailing certification courses. Active women's sailing program. High performance J/boats, spinnakers, racing program.
US Sailing and US Powerboating certifications courses. Cruising Catamaran and Cruising Powerboat courses offered year-round.
American Sailing & Recreational Power Boating Association courses. Live aboard classes in San Juan Islands. Offer women-only classes.
US Sailing certifications courses and active racing program in Kirkland.
Held at the Marine Technology Center in Anacortes, WA. Variety of classes of interest to cruisers, including hands-on boat maintenance and repairs.
Evening Recreational Boater classes. Basic Navigation and Safety,Knots and Line Handling, Transiting the Ballard Locks (on the water training). State of the art maritime training facility.
Full and half day courses at the annual Seattle Boat Show, taught by respected professional sail instructors.
CWB’s Maritime Essentials Series covers a variety of topics that every smart boater should know.
Here are some other options, below.
Also, We have some GREAT non-profit community sailing programs in Seattle, like the Center for Wooden Boats and Sail Sand Point that are inexpensive ways to learn to sail. They are listed in the "Community" page under "Us".
On-line Navigation, Marine Weather, Radar, and Navigation Rules training. Rigorous, high quality training, used by both professional and recreational mariners.
Many more options listed here. From 48 North, which also publishes a current, detailed list annually in January in their magazine.