The meter.
Metres
there are many different ways but I would go with yards.
By hours and minutes.
(1) One way would be to have a stick, stuck vertically into the ground. Measure the length of the shadow and the length of the stick. The actual height of the stick will be a ratio of the shadow's length. Then measure the length of the school's shadow. The height of the school in comparison with its shadow length will be same ratio as the height of the stick compared to its shadow length. You could use a tape measure for this. And possibly a calculator, which will make the calculation easier than doing it by long arithmetic or mental arithmetic. (2) Another way would be to use something that can tell you, from a short distance away from the school, the angle between the top of the school and the ground. A sextant can do this. It is more accurate than using a protractor. Using trigonometry and the distance from the building to where you are standing, you will be able to calculate the height of the school, because it will be at right angles to the line from you to the school. If you don't know trigonometry, method (1) will be easier.
The meter.
Yes
I would use meters.
Metres would probably be the most convenient.
You would typically use a measuring tape or a ruler to measure the length of a school hallway in meters, centimeters, or millimeters. If you need to measure longer distances in kilometers, you might use a measuring wheel or a GPS device.
A rule doesn't exist !
Assuming that the hallway is 30 m long. 30mx100= 3000 cm . Then divide 3000 cm by 2,54= result: 1181,1023622047244094488188976378 in = (Firstly you have to use any measuring tool to find the length of the hallway in meters, or you may get the final reading in inches if the measuring tape tool has divisions in centimeters and inches. Usually they have divisions on foot and cm)
Metres
You could use the centimeter (cm) or meter (m) unit to measure the length of a desk at school.
most likely not. Depends on the size of the school bus and the size of the tape measure. Other than that, I don't know
A high school hallway is crowded.
there are many different ways but I would go with yards.