Along the lines of the snowplow parenting, learning how to learn--what is often called critical thinking, although it's really more than just that--is one of the most important skills for kids to acquire. This requires that parents not explain everything to their kids, but push them to learn for themselves. This can be a challenge for some parents, who feel that 'good parenting' is teaching them.

We sometimes force kids to learn stuff they're not interested in, and they come to hate learning. They endure it because it's expected of them. School sucks for most young people. It's one of the reasons homeschooling is growing. Most kids actually love to learn, or would, when it's stuff they care about and find interesting. Instead of nurturing their inquisitiveness and ability to learn on their own, schools tend to force information down their throats, which information they store in memory for just long enough to regurgitate on the exam.

Not sure how this is supposed to make you feel better. Perhaps it's that it's not your fault that your kid is having a hard time learning--it's probably because he's not really interested in what he's being forced to learn. Or maybe it's that, by getting frustrated, you're pushing your son to learn how to learn instead of breaking it into such comprehensible pieces that any dummy could comprehend, which would likely put him at a disadvantage when trying to assimilate higher education's fire hose of information. Either way, at least you're trying to be a good dad, and that's something.