Welcome to Gaia! ::

I was so much less intelligent as a child, though it could be that my intelligence was simply tempered by massive immaturity. I do see a correlation, in any case. Others around me, mostly teachers often remarked on my perceived intellect, but I am forced to wonder why. It is clear, in any case, that I always looked at things differently.
As for how intelligent I am now... I believe that you all know me well enough and a simple perusing of nearly any thread here should give you a fair idea of my metal abilities. I may be slightly more given to humility now than some time ago, but all else aside, I feel it best to let you make that decision rather than to make it for you. I already have my own estimation of my intellect and others seem to collaborate it.
Intelligence isn't what you know. It is how apt you are to learn and to figure things out. Testing knowledge is typically regarded as a fair way of testing knowledge, because if one is given a decent education then they are believed to know certain things. Make no mistake, however; intelligence is more than just retention.
Intelligence cannot so much be "lost." An inactive mind will become less alert, certainly, and thus less able to learn, but with a regular workout (just like any other muscle) the brain can once again become more able, or even "fit," if you will. The only real way that I can speak to that one can "lose" intelligence is with the entropy of old age. This is rather an over-simplified way of looking at things, however. "Gaining" intelligence is much the same. Keeping an active mind (be it with an education, puzzles, intellectual games, or the like) will certainly set you ahead of one's peers who did not have the same thing.
Granted, I do feel that there are other factors involved. There are certain foods that a mother can eat while pregnant that are believed the raise or lower post-natal brain activity, and I feel that the effects of coming from an environment where intelligence is revered, respected, and personally encouraged should be rather evident in the effects that it typically has on an individual. Mainly, being intelligent is almost as much a choice as it is a happenstance.

As for what you're experiencing, it often happens that a sort of evening-out of intellects (or at least academic performances) occurs. Some children are far more prepared for education in the early years than others. Let's not deny, however, that (to put it in simplest terms) kindergarten and first grade especially tends to be remarkably easy, even for kindergarteners and first graders. It's as much for the sake of getting kids that small out of the house, used to the routine, and among their peers as it is about actual learning.

Eh, my intelligence has never really worried me. I'm of above average, but not insane intelligence, and school was never too hard for me. Learning is my element, but it's more historical and literary, rather than mathematical or scientific. Admittedly I'm relatively proficient with my biology and my chemistry, but physics has always stumped me. Even now my friends come to me for help, and we're at university now. I always remember in my final year of highschool, my best friend always used to copy my work. Towards the end of the year, I decided to shield my art history work, and the teacher told me to play nice, because if my best friend couldn't copy my work, then she wouldn't pass her exams.

When it came to revising and general notes, yes. When it came to exams and assignments, no. Pao's Art History notes looked almost identical to mine during Year 13.

I was always considered to be gifted. I started reading when I was three years old, and I was reading my brother's high school lit assignments when I was in third grade. I was exceedingly verbose, and I spent nearly all of my time reading as a child. This is not to say that I didn't do well in math and science class, as I did, with the exception of high school physics, but I am much more interested in literature and language arts.

In college, we were only allowed to take four classes during fall semester of freshman year, and I was bored out of my mind. For most of my college career, I took six or seven classes, receiving As or Bs in nearly all of them.

So, I was always able to receive good marks in classes. I'm book-smart. I have little to no common sense. I never question how things work. I hate hands-on learning. I would much rather sit down and be asked to write an essay than be asked to perform an experiment. Does this make me any less intelligent than an engineer? I don't think so. I simply have a different type of intelligence.

I'm considered to be rather intelligent. Though I have trouble with schoolwork, which is largely due to shear laziness. As a child I was always top of my class in all of my classes. I had always held straight A's, and did all of the extra work regardless. I was spoken to as if I were an adult from the very moment of my birth. I was not only reading when I was but a toddler, but also playing many video games. (The first of which being Resident Evil).
During Middle School I hit a deep depression. I lost all interest in most everything, especially my education. This went on for a little over a year, eventually I was left with no choice but to drop out of public school and begin home schooling. As it is extremely difficult to motivate yourself or get any sort of help when you are being taught from home, my education suffered. For 2 years in fact.
I do not believe I have lost any of my knowledge nor do I believe that to be possible. I simply feel as if I had missed out on my education. Do I believe I could be more intelligent if I had not hit my depression? Yes, I do.

I never really put much thought into measuring my intelligence. I always did well in school, receiving multiple awards and making the honor roll. I was also inducted into the National Honor Society though I never went to any of their meetings. Languages and literature were my strongest subjects but I did well in all my classes. (Well, other than Honors Geometry but that was because the teacher was half-deaf and smelled terrible so I refused to ask for help when I needed it. He got way to close for comfort any time you had to talk to him.) I know I have lost a lot of what I learned in school from lack of use but I'm a quick learner so I know if I needed to get it back I would be able to fairly easily with just a bit of review. My curiosity is easily piqued and I enjoy learning new things so if being intelligent is having the ability and the desire to learn then I suppose I am.

That's true and while I don't think education and intelligence are the same thing I do think that intelligent people tend to be the ones who more often strive for education, not just as a means to an end but because they genuinely want to expand their minds. That said, I thought about it for quite awhile and just couldn't think of a way to measure intelligence, knowledge is easy to measure but I think intelligence is more internal, less what you think and more how you think which makes it much less quantifiable. In any case that's why I chose to use education as a measure for intelligence, it's not very accurate but it was the best I could come up with.