How do you hack into the computer in the school in Fallout New Vegas game?

Hacking first requires a high enough Science skill, for example one with an average difficulty rating needs Science 50, then 75 for Hard and 100 for Very Hard.

If you've got a high enough skill, simply 'use' the computer and you'll be taken to the hacking interface, which has several Words (higher difficulty gives longer Words), these are the possible passWords, you have to work out which is the right one.

Selecting one will have the game tell you how many letters are in the correct position, but not which positions are correct. So if you select WATER, and the correct one is WASPS, you'll be told you have 2/5, but you won't know which letters. You have to start eliminating other wrong answers by comparing them to ones you've already chosen. For example, you would know WAGER is wrong because it would match 4/5 to WATER, and only two should be correct. However MOTOR is a possible one, so you'd try that next. It has 0/5 from WASPS though, but each wrong answer gives more information.

You can only get three wrong though, a fourth will lock the terminal, although there's a perk that lets you have another go.