Preposition use is difficult for all students, no matter if they are beginners or advanced. Sometimes all we can do as teachers is tell them, “that’s just the way it is.” There are however a few simple rules that might help your students.
IN/ON/AT for Location and Time
We can think of this being organized in a pyramid. At the bottom is IN, which we use for the broadest categories. When speaking of location, we are IN a country, a state, a city or a neighborhood. ON is used for a narrower category—we are ON a certain street. AT is the most specific of the three. We use AT for a specific address.
Intercambio is IN Colorado, IN Boulder.
It is ON Walnut St.
It is AT 4735 Walnut St.
When we are talking about time, the same relation holds true. We use IN for centuries, years, months. We use ON for a specific day, and we use AT for a specific time.
Intercambio was founded IN 2001.
This year, our Comedy for Cambio fundraiser will be IN April.
Comedy will take place ON April 21st.
It will start AT 6 pm.
IN/ON for Transportation
In general, we use ON for means of transportation that hold many people. We typically say we are ON a boat, ON a bus, ON a ship.
We also use on for things that we sit on like ON a bike, ON a motorcycle, ON a horse.
We tend to use IN of for smaller enclosed transportation, such as IN a car, IN an Uber.
IN/AT for Public Buildings
We tend to use IN if we are talking about someone doing the normal activity there, or being there for the purpose for which the place was made.
Mary was IN the hospital last week.
Tom was IN prison.
My daughter was IN school last week.
We tend to use AT, if someone was just visiting the place.,
I was at the hospital last week to visit Mary.
Tom’s lawyer was at the prison meeting with him yesterday.
I was at school for a parent-teacher meeting.
Another difference occurs when we think of the place as 3-dimensional (use IN) vs. 2-dimensional, such as a point on a map.
Lou works AT the supermarket. He works IN the produce department.
When teaching your students, don’t teach all these rules at once. Bring them up in context if you feel they will be helpful.