Cassidy was born August 22, 1856 at Morristown Tennessee the son of Martha Matilda (Jackson) Cassidy and Jeremiah Alexander Cassidy. Cassidy's father was an educator of some note from Virginia.
The descendants of M A Cassidy tell a story from his youth that they say shaped his character and influenced his later life as one of Kentucky's most influential educators during the progressive era.
During the Civil War, when Cassidy was still very young, he served as a Confederate soldier. One day he came home to see his mother. Union soldiers were patrolling in the area and came to her home in an attempt to find him. His mother, Martha Matilda, saw them coming and had Massillon climb down into the family's well with the cedar wooden bucket and windlass to hide. When they had finished searching, the Union Captain asked Martha for a drink of water.
Massillon's mother said, "On one condition. Provided that I can have the first bucket load."
When they drew the first bucket up with Massillon in it, the Captain said, "Madam, I am a man of my word. You can keep the first bucket load."
Cassidy was spared by kindness and the meaning of a man's word.
Cassidy gained his primary education in private schools and graduated from the Reagan High School for Boys in Morristown and later received a Master's Degree from UK. He taught briefly in Tennessee, studied law in Knoxville, passed the bar and practiced for two years before becoming a journalist.
He was elected Superintendent in Fayette County in 1885. Cassidy was "so popular and successful" that he was reelected to five successive four-year terms, and for four of those years, he held joint superintendency of the county and city schools.
On June 4, 1899, the Lexington Leader reported that a "Cassidy Club" was formed to advance his candidacy for Superintendent.
The friends of the candidacy of Mr. M A Cassidy for the Democratic nomination of State superintendent of Public Instruction met last night in the Circuit Court room and organized a Cassidy Club, having for its object the furtherance of his interests regardless of the governor's race.In 1901, Cassidy resigned from the county position and remained superintendent of the city schools. During his tenure, he increased enrollment "from a few hundred pupils to about 7,000." Kerr writes,
"The City of Lexington has long enjoyed the reputation of having one of the best administared and most up-to-date systems of schools found anywhere in the country ... and was one of the first cities in the United States to reorganize its schools on the 6-3-3- plan."Cassidy also implemented:
- "open air schools"
- the penny lunch
- a community center with a swimming pool and auditorium
- manual training
- "domestic economy"
- "opportunity classes ... for irregular children"
- junior high schools
- "kindergarten in all white schools adn some of the negro schools"
- laundries in the basements of schools for both children and parents"
- "moving picture apparatus"
- opened building for community use
- clean and well-kept buildings
- condemned nearly every school in the county as his first act as superintendent
- held the first county graduation ceremonies in Kentucky
- employed teachers who were college graduates
- authored Golden Deeds which served as the text for a character education program in Lexington
- formed the Fayette County teachers' Normal Institute in 1887
- was described in the Lexington Leader as "familiar to every teacher n Kentucky"
- appointed a Catholic school trustee in 1896
- formed the Fayette County Colored Teachers' Institute in 1901 with Prof J H Johnson.
- removed the colored board of trustees for not reporting school census
- was regarded as the father of Kentucky's progressive school laws form 1993 - 1905.
- served as President of the Kentucky Education Association and was active with the NEA.
- served as President of the Southern Association
- authored numerous articles and was recognized by the American School Board Journal and St Nicholas Magazine
- was a member of the Democratic Party, the Masons and the Presbyterian church
- Called for tax increases to better suport the schools on several occasions
- died December 22, 1928.