When I was in grade school math class always started with a sheet of arithmetic problems to quickly solve in class before we even started our daily lesson. The idea was that we needed daily practice because being able to quickly add, subtract, multiply, and divide was an essential skill. Now calculators and computers have made this ability obsolete because nobody is tasked with doing a lot of arithmetic by hand. In high school I learned how to calculate square roots by hand and how to use a slide rule which are more tasks that are obsolete. I'd argue that if a certain task can be accomplished with a key on a calculator than being able to do it by hand is also an obsolete skill. As an exercise to understand the concept you might work through a few by hand but once understood abstract and automate it. If we need to limit students to crippled calculators than perhaps we are teaching the wrong things. The one time I'll admit to cheating in college was in statistics. After an entire semester of allowing any calculator in class or for tests my professor informed us on the morning of the final exam that if we had an advanced calculator we were only allowed to use it as a 4 function calculator. If he warned us before the exam I would have been able to memorize the necessary formulae but his sudden requirement was so unfair that I cheated and used the statistical functions of my calculator with a clear conscience. Had I crammed for the exam and memorized the formulae for the exam would I still remember them today? Of course not and nor should I clutter my mind up with what is now trivia. I do see some advantage to standardize for classrooms but were it up to me I'd have kids use Wolfram Alpha on their phone, tablet, or laptop. Cheap, easy to use, and powerful.