Ignore your 'teacher'... :)
Intelligent: having good understanding or a high mental capacity; quick to comprehend, as persons or animals.
Notes: people are intelligent ; statements (words) are intelligible. Intelligent often suggests a natural quickness of understanding: 'an intelligent reader'. Intellectual implies not only having a high degree of understanding, but also a capacity and taste for the higher forms of knowledge: 'intellectual interests.'
Source: Intelligent | Define Intelligent at Dictionary.com
The people from that site are created by more than 1 intelligent person. So which source is better? :D
Hope this helps.