Jacksonville, with the land areas of 885 square miles, is the largest city by area in the contiguous United States, and it is also the largest city by population in the state of Florida. In the recent years, even through the struggling economy, Jacksonville has continued to attract a talented workforce here and the population has continued to grow each year.
Every big city has some negative issues, that does not mean that everything about that city is negative. Depending on where you choose to live in or around Jacksonville, you can get the “big city feel” or the “small town feel”.
As far as your question about schools, St. Johns County (county south of Jacksonville) has some top rated schools: http://www.greatschools.org/florida/st-augustine/St.-Johns/