Due to my teaching style I found that some scientific calculators work better than others, here are some suggestions:
Make sure the package states SAT or AP approved and has the word Scientific.
All Texas Instrument (TI) scientific calculators and graphing calculators work well with my teaching style except for the TI 30XS, see image below:
instead, consider the following TI 30XIIs which my students found the scientific notation key easier for them to use, see above image.
Also, another calculator that works well with my teaching style is the Casio fx 300ES Plus which comes in Black, Silver, Blue, and Pinks, see below:
It is not required by the math or science departments to have a Texas Instrument, and/or Casio scientific/graphing calculators, or another brand. Since our math department tends to use TI products, I believe your child should use what will make them successful in math.