A Student microscope is a low power, durable optical microscope typically sold in bulk for use in school science classes. Although university science students use microscopes, the term typically refers to the type of instrument used in primary and secondary schools. For most non-scientists, the only time a microscope was ever used was in a school science class, and so when many people picture a microscope, it is a school microscope that comes to mind.
The classic school microscope, as was common in American public high schools in the second half of the 20th century, was a low power (3-10x) double lens instrument, with an eyepiece adjusted with twin knobs, one for coarse and one for fine focus adjustment. The primary lens was often mounted on a rotating platter so that different lenses could be rotated into the line of view (typically there was a choice of three different powers). The optical quality of these inexpensive microscopes was very poor, so that choosing the highest-power (and thus longest) lens was often quite useless. Due to its length, the highest-power lens often crushed the slide beneath, as the hapless student rotated the focus knob vainly trying to see something and collided with the slide, which was held in place by small metal clips. Beneath the slide was an adjustable mirror, or later, a battery powered light bulb.
Thus the student microscope was very much like any other two lens optical microscope, but is distinguished from others by its low cost and durability.
Despite its poor relative quality, the student microscope has an important place in the history of microscopy. It was "invented" (or rather, marketed) after World War II at the urging of a young Bausch & Lomb marketing manager, Herbert J. Mossien, who recognized the commercial potential of a mass-produced microscope which could be sold in bulk to schools. Up to that point, microscopes were precision instruments that were typically quite expensive. The student microscope was a huge commercial success for Bausch & Lomb, and its massive sales to high schools, with a renewed emphasis on science after the Sputnik launch, propelled Mossien to the head of the company's Scientific Instruments Division and to the eventual rank of Executive Vice President. Mossien retired early from the company to become a marketing professor at Rochester Institute of Technology, and became a well-known after-dinner and motivational speaker.
Thanks to the student microscope, almost everyone with a basic education in the industrialized world has been taught to use this formerly esoteric instrument, and has seen formerly invisible structures such as cells firsthand.