Scientific calculators are helpful beginning in upper-level arithmetic, but you want to avoid calculator dependence.
Teachers typically determine how much emphasis to put on calculators. It’s important that students are strong in a technique (such as multiplication, or graphing a linear inequality) before they are allowed calculators that do the technique for them.
In general, calculators should be used only to save time, after the relevant concepts are learned thoroughly. Basic formulas should be memorized.
With the above guideline in mind, seek scientific and graphing calculators with functions that are appropriate for the course or grade level. Keep in mind that AP tests, ACT and SAT, and other standardized exams have “prohibited models” of calculators and very specific rules concerning calculator use.