What is the name of the First Doctor's human companion who was a science teacher?

What is the name of the First Doctor's human companion who was a science teacher? The answer is Ian Chesterton. Ian is a human science teacher from Coal Hill School who becomes one of the Doctor's first companions in the original Doctor Who series.

Ian works alongside history teacher Barbara Wright, and both become concerned by their student Susan Foreman's unusual knowledge. Their investigation leads them to a junkyard in London, where they discover that Susan's grandfather, the Doctor, is travelling in a police box that is actually the TARDIS. Ian and Barbara are then swept into adventures across time and space.

Played by William Russell, Ian appeared with William Hartnell's First Doctor from the programme's launch in 1963 until 1965. He was practical, physically capable and often acted as the group's protector, while also challenging the Doctor's dangerous curiosity. His scientific knowledge helped the travellers solve problems, though he was not a Time Lord or an alien.

Barbara Wright is the companion most likely to cause confusion: she was also a teacher at Coal Hill, but taught history. Ben Jackson and Steven Taylor joined the TARDIS later, after Ian's era.