Don't get me wrong, I like macs, but for my HS kids I bought rather inexpensive laptops $300-350, with the best deal I could find at slickdeals.net
In a HS backpack they are going to get banged around, possibly stolen, etc.... and it only has to last two years. Max out the ram, memory is so cheap these days. You will probably need to get a new one for college, with my kids the schools had specific requirements for the computers.
Even the cheap laptops are powerful enough to run most software..... my two year old $300 Toshiba runs Solidworks fine.
Or check the Dell outlet, and sometimes you can find a 20 or 25% off coupon on Slickdeals. That's how I bought my last laptop:
http://outlet.us.dell.com/ARBOnlineSales/Online/InventorySearch.aspx?c=us&cs=22&l=en&s=dfh&brandid=2201&fid=914