A mechanism or CraftBukkit plugin to not allow building or mining in Minecraft?

PermissionsEx and ModifyWorld should solve this problem quite nicely.

PermissionsEx is a general permissions plugin and ModifyWorld is an optional part of PEX:

[ModifyWorld] provides the possibility to control players abilities, such as destroying/placing blocks, riding carts/boats or even getting spotted by mobs and much more. Disabled by default.

The PEX wiki has a nice series of articles explaining exactly how to setup PEX with modofyworld. I suggest you follow along the tutorial so you understand how to install and configure PEX. Then when you get to the "Basic-Permissions-Setup" page, use my suggested configuration instead of theirs.

config.yml:

permissions:
    backends:                            <- Backend Definition Section
        file:                            <- File Based Backend Section
            file: permissions.yml        <- File Name To Use
    backend: file                        <- Backend To Use On Start
    superperms:                          <- Settings For SuperPerm Support
        enable-wildcards: true
        disable-unmatched: false
        enable: true
        debug: false
        compatibility-mode: false
    createUserRecords: false             <- Other Settings
    allowOps: false
    debug: false
    basedir: plugins/PermissionsEx       <- Directory Name To Use

Once this is done, it sounds like this ought to work as your permissions.yml:

groups:
    #default group
    default:
        default: true
        prefix: '&0(&4Default&0)&7 '
        permissions:
        - -modifyworld.*    #All permissions, equivalent to current setup

    #students
    students:
        default: false
        permissions:
        - modifyworld.chat
        - modifyworld.sneak
        - modifyworld.sprint
        - modifyworld.blocks.interact.69    #Allow levers
        - -modifyworld.*

    #teacher
    teacher:
        default: false
        permissions:
        - modifyworld.*
        - permissions.*

users:
    SomeStudent:
        group:
        - students
    SomeOtherStudent:
        group:
        - students
    YetAnotherStudent:
        group:
        - students
    at01:
        group:
        - Teacher

This puts the listed students into the students group, which denies all permissions except those specifically listed. You may want to browse the block ID list and allow modifyworld.blocks.interact.<Block ID> with some more of them (e.g. chests, buttons, doors). Make sure to use the "Dec" value listed, not the "Hex". You may also want to browse the permissions list to check for other things you want to allow students to do.

If you miss any student names they will be allowed to do everything, which is equivalent to the permissions they have right now. If any students are in this group when they chat their name will be prefixed by "default" in coloured letters, which will alert you to fix this error. You can fix this by typing in game using your op account:

/pex user <username> group add students

Note: I specifically did not make the default group the limited one for students. PEX often messes up plugins by trying to apply permissions to the actions of the plugins (so in this case ScriptCraft might have the same limitations as the students). I have no idea if this is a problem for ScriptCraft, you could test it by moving all the student permissions to default and seeing if ScriptCraft still works.

In Response To Comment: I've modified the config to account for all students needing to be op. By using allowOps: false this tells PEX that it should apply permissions rules even to ops. With this setting on you will probably need to allow access to all of the ScriptCraft commands, simply add the relevant permission nodes to the relevant groups.