Code:
BEGIN{ print "Name Test1 Test2 Test3 Average Grade"}
{avg=($2+$3+$4)/3;
avgtest2+=$3
avgtest3+=$4
if (avg >= 90) grade="A"
else if (avg < 90 && avg >= 80) grade="B"
else if (avg < 80 && avg >= 70) grade="C"
else if (avg < 70 && avg >= 60) grade="D"
else if (avg < 60 && avg >= 50) grade="E"
else grade="F"
printf("%-8s%-8d%-8d%-8d%-8d%-8s\n",$1,$2,$3,$4,avg,grade)}
END{
printf "Average%-8d%-8d%-8d\n",avgtest1/NR,avgtest2/NR,avgtest3/NR}