Sorry, I forgot to comeback to check on this thread.
I live in Brandon, which is a suburb of Tampa. Hillsborough County is one of the largest school districts in the nation, and honestly, at times can be a hot mess. I know more about elementary because my mom is an elementary teacher. But I also know that the middle schools in my area are not the best. DD will be in 4th grade next year, but the talk has already begun on where she's going to school for middle.
We currently have her in a "C" school, but it was an A school two years ago. Two years ago they did a massive overhaul on how the FCAT was graded, and the school's grade plummeted. The first year, it should have been a "C" but by law it wasn't allowed to fall more than two grades at a time. Now, I'm not saying that there aren't better schools out there, and her school is a little rough around the edges, but the teachers are really good. We have her there because my mom works at the school, the school we are zoned for is actually an "A" school (soooo, we're probably not the norm in the area). I'm probably one of the only people you'll meet who will tell you not to base your total decision based just on grades.
Here in Hillsborough County, the first application period for choice is before Christmas, there's one generally in the spring, and one over summer. There is an pre-IB program at William's Middle here in Tampa, but a lot of the spots do go during the first application period. Our magnet and IB programs are generally held at schools that are in the lower income areas ... and you should also factor in drive-time/bus time for the kids as well. My parents live in Plant City (which is about 15-20 minutes away from Brandon) and my sister was interested in going to Blake which is the performing arts high school, and her bus was supposed to pick her up at 5:30 in the morning. She chose to go to school closer to home, but still not her "home" school, because she didn't was a 3 hour bus ride to school and back each day. My daughter will be going to Progress Village, if we stay in the area, for middle school because she is interested in the performing arts program there as well. From what I understand, we can chose any middle school in the county that isn't capped, but we have to provide transportation to the schools outside of our region. The two middle schools closest to us are considered to be very rough, and the one next closest to us is known for it's issue with pills. Middle school, and they have issues with drugs, oy! And we live in the middle of the suburbs ... it's not what parents expect.
The Fishhawk area is the closest area to me that has consistently high scoring schools, throughout elementary, middle and high school. Like a PP poster said, there isn't an entrance exam to get into the IB program, you have to apply and hope to get in. I will say that Strawberry Crest is the newest IB program here in Hillsborough, it just opened up about 2-3 years ago. It's a lot closer to Fishhawk than King is, and is in a much better part of town.
I probably gave too much info without giving enough at the same time. If you have any specific questions, I wouldn't mind asking my mom if she can help. I know nothing of Pinellas county ... but this is their website.
https://www.pcsb.org/
I also don't know much about Catholic High schools in the area. My friends attended Tampa Catholic
http://www.tampacatholic.org/ back when we were in school and I had friends who attended Jesuit (the all boys school)
http://www.jesuittampa.org/.
Nativity Catholic runs from elementary to middle
http://nativitycatholicschool.org/ and I think St. Stephen's does as well
http://www.ststephencatholic.org/school/. I'm sure there are more than that, but I only know of these by names.
http://www.sdhc.k12.fl.us/ - This is Hillsborough County's website.