#!/bin/bash
# Richard Ferguson Unix/Linux CS121

user=0
score=0
count=0
sum=0
highest=0

# set 'smallest' to a real high number, so the first number you read is always smaller!
smallest=99999


# This is wrong.  You need spaces.
# Also, use = instead of ==.
# until [[$user=="done"]]

until [[ "$user" = "done" ]]
do
        # No point doing this stuff here.  Do it ALL inside your 'score' loop.
        # echo -n "Enter Score : "
        # read score

        # This is wrong.  Needs spaces.  Also, =.
        # But you might as well just do an infinite loop.
        # until[[$score==999]]
        while true
        do
                echo -n "Enter Score : "
                # you forgot the read
                read score
                # Instantly break the loop if we get >= 999.
                # && is a short-form if/then.
                # Much easier to read than if [[ "$score" -ge 999 ]] ; then break ; fi
                [[ "$score" -ge "999" ]] && break

                # Variables don't work that way.  Use $(( )) for math.
                # sum + = $score
                sum=$((sum+score))

                # Much easier ways to do this.
                # if (( $score > highest ))
                # then
                # highest = score

                # && is a short-form "if".  [[ condition ]] && thing-executed-if-statement-is-true
                # There's also an || which does [[ condition ]] || thing-executed-if-statement-is-false
                [[ "$score" -gt "$highest" ]] && highest="$score"
                [[ "$score" -lt "$lowest" ]] && lowest="$score"

                # No reason to nest three 'ifs' here.  No reason to check for 999    inside
                # them either.
                # if (( $score < lowest ))
                # then
                # lowest = score
                #    if (( $score -ne 999 ))
                #   then
                #   $howmany+ = 1
                #    $sum+ = score
                #    fi
                #fi
                #fi

        # you forgot every one of your 'done's.
        # You should have one to match the end of each while/until/for, 
        # just like fi's match if's.
        done

        echo -n "Type 'done' to finish: "
        read user
done
# again, math doesn't work this way.
# avg = $sum/$howmany
# You can embed $(())  math in the middle of things, usefully.
# You don't need -n to print more than one thing.  Just put more than one thing into echo.
echo "average $((sum/count)) sum $sum highest $highest lowest $lowest"
echo
echo "Goodbye"    
exit 0