Not much - at least I don't know much - and in all likelihood there isn't much to know. I couldn't find accounts of his former students (they would have been children though, learning their abc's with him more or less) in De Felice (it is possible they are included in contemporary biographies - I'll see if I can find something).

As for why he had become a teacher. Mussolini wasn't wealthy but he had received a decent education. As he himself put it, he had gained "a piece of paper worth make a living out if it". Hence in 1901 (being eighteen years old and fresh from graduation) he made demand for the position of school teacher in a few towns (some rather distant - he did want a job) but was turned down.

We were - he wrote to a friend of his - thirty two dogs with four bones to share.

A similar attempt to find a job as "substitute assistant" (an office clerk) in the town administration of Predappio was rejected.

Thus Mussolini spent his first year after graduation more or less unemployed. In February 1902 he was appointed substitute teacher for the 2^nd and 3^rd classes, male school of Pieve Saliceto (a fraction with socialist administration that might have received word from Alessandro, Mussolini's father, who was a small socialist leader) and held the position until the end of the school year.

It was a decent position, a decent job (with the perspective of a confirmation) with a somewhat low salary, that nonetheless allowed for integration with private lessons. At the end of the year though, he was let go (or rather he left, because he knew they were letting him go), and despite a few biographers crediting "political" explanations, the cause was - as he himself admitted, not without a certain complacency - that he had been having a public affair with a married woman. He then moved to Switzerland, where he remained until the end of 1904.

Back to Italy, he settled his obligations with the Army and then took up the position of teacher again, in Tolmezzo, nearby Udine. Teacher's duty - even less than before - did not appear to satisfy him.

Since the first days - he said in his biography - I realized that teaching was not the best job for me. I had the 2^nd class [seconda elementare], with forty vivacious kids, a few of them irreducible and dangerous brats. There is no need to say that my salary was very modest. Only seventy five Lire a month. I did my best to keep my class going, but with little results, since I had been unable to solve the disciplinary issues since the beginnings.

Again, Mussolini was let go (or left), because of the public dissatisfaction over his public affair with another married woman.

Another year went by, until he found a new position - this time a better one, as French teacher (he had passed his license examination in November 1907 but failed the German one) - at the public boarding school, U. Calvi, of Oneglia (not far from the birthplace of socialist leader G. Menotti Serrati and home to his two brothers Lucio and Manlio) where he also begun his return to political activity after his Swiss experience.

It might be correct to say that it was around this time - but more likely during his sojourn in Trent during 1909 - that Mussolini started to look for a future career as a journalist-politician (rather than just for a job - even his political experience in Switzerland had been in large part occupation driven).

He had been let go from Oneglia as well (despite what credit his relations with Menotti Serrati could earn him there) - I don't know of women there though.

Broadly speaking, Mussolini's early years weren't exceptional in a formative sense: he wanted a job, aspired to recognition, looked for a way to earn some (let's avoid the obvious pun). It's only at the end of his teacher years that he appears to become more "politically oriented". Despite the attempts to tie the origins of Mussolini's beliefs with his erratic occupational experiences made by a few of his biographers, there isn't much to see but one guy who can't keep a job, and has no special commitment to it, until he finds one which suits him more.