Helicopter parenting, now with extra math! Don’t bore about this at the next PTA meeting, let the kid do his homework, it’s clearly intended to get them do some additions
Tell a senior person at the company, or the Human Resources person you dealt with. Tell them what you experienced... this is unacceptable behavior and The hiring firm should know.
Being a software developer is a unique profession, since many software developers never received much formal training. For instance, many mathematicians, physicists, (non computer science) engineers write software for a living. Compare that with structural engineers, lawyers or medical doctors: it is very different.
Because of that, I firmly believe many people can work as a software developer and contribute meaningfully to a company's bottom line.
State your ambition and let the results of your work do the rest.