I'd been toying with the idea of what RPN calculator a kid could use at school here in the UK. I thought the sticking point would be that most RPNs are programmable, but turns out that isn't an explicit exclusion on the JCQ calculator guidance for GCSE and A-level exams. They can also use graphic calculators. There is a hard no on CAS. The HP-15c seemed the least likely to cause issues with invigilators, so went for this. We'll have to see if it works out though.
He really likes it. The titanium back has given a great looking engraving of his initials. Now just hoping he didn't lose it!