What does the dress code “smart formal” mean?

[NotUnderMyUmbrella]

It’s for a 6th form prize-giving ceremony, held in the evening, dress code is for the students.

Can’t decide if it means formal, as in boys in dinner jacket-black tie and girls in glamorous full length dresses, similar to prom.

Or smart, which I would interpret as boys in suit/jacket and tie, girls in smart skirt and blouse, trouser suit or corporate-looking plain dress perhaps with a jacket.

Or something between the two, which would be..?

It's verging on unethical to insist on a suit. Cotton chinos style trousers and a cotton shirt are easy to find and can be worn again, but a one off suit? Probably, for many, it'll be a cheap, fast fashion polyester, which will look less smart than chinos and a shirt.