Intelligent quotient can be measured based on many factors.

A high level of education can amount or result in a good level of intelligence. However, it depends on many factors. We all have different backgrounds with maternal and paternal IQ that is not the same. If both parents have a high level of intelligence quotient, their offspring have a high probability of having a well-functional IQ. But the development requires some form of training for it to be productive

Education is an opener of IQ. Sometimes, a well-educated person with an average IQ might do better in some areas than another person with a high IQ because of exposure

In schools, people with lesser or lower IQs seem to learn slower than those with high IQs

Intelligence is inbuilt but school has a great role to play in unlocking many parts of the brain that works to make us (human) act/talk intelligently

Conversely, I would also say that it's not mandatory to go to school before people can notice that one is intelligent. I think I have a short true-life story to back this up

My mother's friend was a stack illiterate. She can neither read nor write but she could produce many things like Automatic transmission fluid, perfume, Car coolant, brake oil, and so on. She took it upon herself to know all this without having prior knowledge and she ended up having her production company where she produce all these products. The funniest part was that she didn't learn it from anyone

Charles was a secondary school drop out but he became one of the best motivational speakers hosting and educating graduates

These are instances of close pals. Everyone has an IQ but on different measures. If it's channelled through the right path, it would be well utilized

Going to school and truly having a good grade means you are intelligent and I think it's a measure of intelligence in that aspect

Also, learning a skill and having a good knowledge of it is a measure of intelligence on that part too

The measure of intelligence to me is doing well where you find yourself irrespective of beign educated or not