If you want to take an accurate and professional online IQ test you have 2 choices:
http://www.funeducation.com/Tests/KidsISIQ/Kids-IQ-Testing.aspx
http://affiliatetests.funeducation.com/Partners/KidsISIQ001/TakeTest.aspx
Both tests were designed by Dr. William McConochie. Not some guy who's good at programing an ap for amusement but from some guy who's been a licensed clinical psychologist for over 40 years and who has authored several IQ tests, aptitude test and has submitted research papers on psychology.
You will not find any other IQ tests on the web that are as accurate and as professional the two noted above.
Dr. William McConochie has a B.A. from Carleton College, a Master's in School Psychology and Ph.D. in Counseling/Clinical Psychology from IIT in Chicago, and a post-doc in Clinical Psychology from Northwestern University School of Medicine.
He is a member of the American Psychological Society and the Society for Industrial and Organizational Psychologists.
Dr. McConochie has written, edited, or reviewed many of the tests on our website such as the IQ Test, Spatial IQ Test, Career Test, Personality Test, and many others. Look for the PhD-Certified seal.