You should Really keep the current laptop and make a few additions and changes like these below to make it suit Your personal needs instead…
1) Look into what's called an "external battery" for it… They are made to work with Your specific model, and are basically a 2nd battery that connects to the power adapter port on a laptop. They can be heavy and large, but they will double the life of the battery up-times.
2) You should also look into either keeping around a REGULAR 2nd battery for Your laptop that You can switch to between the 2-hour classes, getting You the first class on 1 battery, and then the 2nd class on battery #2… A standard 2nd battery would run about $25 - $45 on Amazon, and would charge in the same laptop just like the battery that came with it. There are also "9-cell" and "extended-life" batteries that are designed to last longer than the standard batteries, and even one of them would triple the time You have now.
3) You can also set up a few "tweaks" that will help conserve serious battery up-times like using a "speedstep technology" setting that will force Your system to use a slower CPU speed when running on batteries, saving the gaming power for when on wall power. You can also remove the CD/DVD drive from the system, and use the last suggestion…
4) You can also set up a 2nd User account specifically for use only during classes that saves battery power… You can actually customize the new account to disable some of the internal hardware like the network adapter, modems, Wi-Fi adapters, CD/DVD drives, and things like running services and updaters that continuously check for online access which drains battery life FAST.
And, if You're using an anti-virus software, an anti-spyware software, pr anything by Norton or most of those "personal firewall" programs, they are a SERIOUS drain on battery life, and if You're only using a system in a classroom, there's no reason NOT to disable the Wi-Fi adapter and NOT run thiose softwares on the 2nd user ID… This step alone could add an extra HOUR+ to the existing battery's lifespan, and with a 2nd battery for the 2nd class… It's looking like Your problem's solved.
The final option would be to actually run something like linux from a USB flashdrive during classes, there are several that can be extremely useful and simple if You look around a little, I personally like Puppy linux, which has several full-featured text editors that can save in many file formats for use on a Windows system later… It may extend Your battery life for simple documents wth things like Bold, italic, colored text, multiple size fonts, etc…
