Can a sheet be made active using AppleScript?

This works for me:

tell application "Numbers" to ¬
    set active sheet of ¬
        document 1 to ¬
        sheet 1 of ¬
        document 1

Obviously, change the value of the elements as appropriate.

You can also use this syntax:

tell application "Numbers"
    tell document 1
        set active sheet to sheet 1
    end tell
end tell

Again, change the value of the elements as appropriate.