In the UK, school refers to education between ages 4-16. (Compulsory) College is attended by choice age 16 -18 University is attended by choice age 18+ All people in the UK must attend school by law. College and University offer further education to anyone if they wish to learn more.

I've heard some American speakers use 'school' to mean University, too. I've looked it up on Cambridge dictionary, which verified that 'school' might mean university or college. However, without the right context, you might be misunderstood here. Dictionary entry: http://dictionary.cambridge.org/dictionary/american-english/school_1?q=school

We in the United States tend to use school for any institution of learning. We have "trade schools" and "language schools". We have "pre-schools" and schools for training out pets. We often refer to universities and "gradulate schools" as "school". I was surprised when someone didn't understand my use of the word "school" to refer to a university. We also use the same word "student" to refer to a person attending a school. Someone can be a medical student or a student in a preschool.

Obviously school and university are two different thing.