There is an important Hungarian story connected with this: Brunszvik Teréz founded the first nursery school in Hungary in 1828, almost a decade before Fröbel invented Kindergarten in Germany. Beethoven taught her piano. She was a great pioneer who dedicated her life to improving education for children and women, and we once saw a statue honoring her, when we visited her home, the Brunswick estate in Martonvásár, Hungary.
I am not a native speaker, so I don't know if it's offensive in English.
But the Hungarian sentence is not offensive, you can call women under about 30 "lány". I can also imagine a situation, where a 50-year-old woman says: "Délután kávézok a lányokkal." "I'm going to drink a coffee with the girls in the afternoon." meaning that she meets her friends, who are women at a similar age.
In Hungarian, could you say Az óvónő egy angol fiú - The kindergarten teacher is an English boy? Although I guess that wouldn't be óvónő...
In English, I think a man might talk about "going out drinking with the boys" and a woman could say she was having coffee with the girls, and it wouldn't be offensive, but it's only for very informal friendly conversation... referring to a professional as a girl or boy would not be appropriate unless the person was actually a child.
The nő in óvónő means woman.
"Az óvóbácsi egy angol fiú." is possible, too. (There's no proper male version of this word (because there are so few male kindergarten teachers I guess), the official gender neutral expression is óvodapedagógus, the not official, informal but actually used word for a male kindergarten teacher is óvóbácsi. Bácsi is something like uncle, kids say it to any adult men. The female version of this is "néni", you can say óvónéni as well.)
To be clear, "fiú" and "lány" are not used in a formal, official context but you don't have to be friends with the person to use them. The parents of the children can say to each other that "Az óvónő egy angol lány." or it would no problem if a university professor would say "Az egyik fiú puskázott a vizsgán." (One of the boys cheated on the exam.), he would not write it in an official report though.