Perhaps my opinion is valid, given that I was recently in high school, and have a brother who is just now a freshman in high school. Given that, I felt at no time during school that my own computer was necessary, and my brother is doing fine without one as well. I'm not trying to say I know how to parent, because I don't yet. I'm just basing this on experience through school. I'm sure if I had asked for a Mac at 11, or even 13-14, my parents would have laughed at me and said buy it yourself. I had access to the household computers, and that was plenty for me.
You realize all schools are different? Curriculums are different. Education styles and educational rankings are different. Im located in one of the highest ranked school districts in the country and i know my nephews need their laptops.