That site must not include freshmen. The Hartselle site shows the 2006 student enrollment at 885. I trust the Hartselle site to be accurate. When I graduated, we had 860...
I think the way Alabama does their classification is by students who are capable of competing in athletics. Handicapped students are deducted along with students over the allowable age and certain others, I am not sure of all of the criteria. Piedmont dropped to 2A under the new classification system and shows an enrollment of 210. When I played, we were a large 3A or small 4A school depending on the year. The actual enrollment numbers right now are around 310 students so appearantly 100 are not eligible for athletic competition.
According to GreatSchools.net, Hoover has 2044 students, Spain Park 1319, and by comparison, Southlake Carroll has around 2400.
Skyline in Dallas has over 4000 students, as do Elsik, Westield, and Hastings in Houston. (there are many more around the state)
Cypress falls has well over 3000, as do Clear lake, Jerset Villiage, Langham Creek, Klein, and Cypress Ridge. (there are many, many more around the state)
You do not have enough fingers and toes to count schools over 2000 in Texas, and as for schools over 1000...think counting on blood cells. Lots of those.
Texas has 21,000,000 people compared to Alabama's 4.5. There are lots and lots of chilluns in school there.