In 1956, MacLean was offered the position of head teacher of Plockton High School in Wester Ross, not far from where his paternal grandmother's family had lived. It was a difficult assignment as the remote location was not attractive to teacher candidates, and MacLean frequently had to teach due to vacancies. While at Plockton, he promoted the use of Scottish Gaelic in formal education and campaigned for a Highers exam for learners of Gaelic. Before 1968, there was no separate exam for Gaelic learners, who had to compete with native speakers if they took Gaelic Highers. MacLean felt that this unfair policy discouraged many students from studying Gaelic, although he encouraged his students to take the exam even if they were not native speakers. In 1966, he presented a paper to the Gaelic Society of Inverness outlining the practical issues in Gaelic education. MacLean pointed out that in continental Europe, it was not uncommon to study three or four languages in school. According to MacLean, Scottish children would benefit from studying three languages in school alongside English, and "surely it is not expecting too much of Gaelic patriotism to demand that Gaelic should be one of the three?" MacLean set high academic expectations for his students and also promoted shinty; in 1965, the Plockton team won the cup for Ross and Cromarty.