I get straight A's in all my courses with MINIMAL effort at my high school(and I'm starting my final year soon) that cares a decent amount about it's academics, so I believe that I am intelligent, but not of genius intelligence.
However grades do not necessarily mean smarts, or lack of. Since there are different areas of intelligence besides academic (Logical-mathematical):
Kinesthetic (physical movement)
Linguistic (language IE: puns, wordplay, diction, etc)
Musical (dealing with....music)
Interpersonal (how you understand how YOU think, react, etc)
Intrapersonal (how well you deal with and interact others)
Naturalist (how well you understand nature)
Spatial (deals with colors, organization, and art)
So how do I fare with each group?
Logical-mathematical: quite good to excellent
Linguistic: excellent (except for when it comes to spelling and rare grammar mishap)
Musical: defiantly above average but perhaps not quite excellent
Kinesthetic: I'd I assume this one is below average
Interpersonal: excellent in this one
Intrapersonal: about average
Naturalist: if i get lost in a forest i know more then enough to get out, but then again so do (hopefully) any decently smart person so a bit above average
Spatial: I barely scraped by in middle school art, and when I 'organize' it doesn't stay that way for long so.. horrible
So yes I suppose I do believe to be an intelligent person
On a side note despite being young(or at least not being a full fledged adult) I have an uncanny attention span of about 55 minutes. FIFTY FIVE minutes, I tested it while enduring particularity boring classes.