I think I'm probably biased, but I would agree that our educational system, and in particular, our public education system holds high importance in our society and definitely has room for improvement. I do think that education is still a really broad topic, so you might consider breaking it down a little more.
It seems like our country's focus has been on the problems lacking in public education - lack of financial resources, safety in schools, overcrowding, schools prone to dropouts, focus on test scores, teacher quality, etc. These are just some of the issues plaguing public education today - ask any one individual involved in the public education system whether it be a parent or teacher, and you'll hear a different answer about what the biggest problem is.
I would choose one area of education to narrow your focus a little more, and then work on addressing just that. Do you think the problem is school safety? Focus on what our nation can do to improve that aspect of education.
In the resources section below, I'm including an article on President Barack Obama's take on education, along with problems and solutions. It might be a good starting point.
I think that education is a very broad topic, and depending on how long your speech is, it may be hard to address in just 5-15 minutes.
The best tip I ever got for a speech had less to do with the content of the speech itself, and more to do with practice, practice, practice (in front of a mirror, a video camera... whatever)!
Education seems like a great topic for your speech and I had found that something that is close to our own hearts and beliefs is the best topics, because you will write and speak about it more passionately. So if education is your choice, then you should definitely go with it.
Idea? Plug Education.com. Many people feel that the lack of performance in schools is due to the lack of interest of the parents, this may be true, but as you can see here on education.com, that many parents are still very involved, very concerned and face many obstacles.
You may be able to approach this from different angles and do personal interviews with parents and students, run statistics of grade performance and social development based on involvement of the parent to see if it actually made a difference. Sounds like interesting research.