This postcard has no message or information on the back, but it came from a dealer in Pennsylvania who specializes in photographs from Imperial Russia (pre-1917). The empire of the Tsars was truly vast, encompassing areas of northeastern Europe and Central Asia which today are made up of independent nations. It’s impossible to say exactly where this photo was taken, but it looks to me like a scene out of a 19th century Russian novel. Since it’s a postcard, I’d guess it was made between 1905 and 1915.
I’d bet that the young man in the straw hat, fourth from left, is the teacher, and the two adults to the left are workers on the estate where the class is taking place.
The children may have been members of the family which owned the estate.
I wonder what kind of experiment they were conducting?