Alcumus might be a better choice for developing mathematical thinking with advanced students, although it might not be quite as useful for the lowest grades.
ALEKS is another option the school might want to consider, especially given that, because of the way the program is set up, they could also use their school subscription for remediation and RTI purposes. It pretests each student and only teaches what they don't already know. It only takes between three and five questions right in a row on a particular topic to show provisional mastery (which is then rechecked on the next test).
Khan Academy is another possibility.
