The main positive aspect of intelligence tests is that they are an easy way to assign numerical values to children’s levels of aptitude. This is the same reason why most standardized tests are useful to some people. Let us say, for example, that you want to place children in a gifted and talented program at your school. How do you determine who is gifted or talented? If you ask the teachers, you will get biased answers. The teachers might only pick children who are outgoing and are willing to speak up in class. They might only select children who have a great deal of knowledge, rather than those who are very intelligent but lack knowledge. In other words, it will be very difficult for teachers to identify gifted children simply from observing them in a school setting. By contrast, if the school uses intelligence testing, it will be easy to identify students who are (apparently) gifted.
The problem with this is that these tests might not truly be testing intelligence. This is the major con of intelligence testing. It is very hard for us to even define what intelligence is and it is even harder to come up with tests that will measure levels of intelligence. This is in large part because it is hard to come up with tests that measure intelligence in ways that do not depend on students having certain types of knowledge. There is a famous example from a standardized test in which students were asked to identify the analogy that was most like the analogy between an oarsman and a regatta. This presupposed knowledge of what a regatta is. This was a culturally-biased question because it favored those people who had grown up in a social milieu in which they would have become familiar with rowing terminology. When questions like this are asked, intelligence tests are biased in favor of people who have certain types of knowledge because of the culture in which they have grown up.
In short, then, intelligence tests are convenient as a way to put a numerical value on intelligence which is, of course, very difficult to define and measure. However, they are not necessarily valid because it is hard to know if they are truly measuring intelligence. This is the major drawback of using such tests.