David - your re-initialization of vecchecker in the while loop uses a different condition than the one outside of the while loop. Note that if
vecgrade = [1 2 3];
vecchecker=vecgrade<0 & vecgrade>10;
then
vecchecker =
0 0 0
Which makes sense because the condition is saying if the grade is less than zero and greater than ten - which is impossible, so the vector is all zeros (false).
Change your re-initialization of this local variable to be the same as that outside of the loop
vecchecker=vecgrade>=0 & vecgrade<=10;
and your code should work fine.
