From how much money a family can expect to spend on a child to the number of hours a student has to go to school each year, education looks very different around the world.

In many countries around the world, autumn means the start of a new school year. But that means something very different if you’re in the US or Chile, Russia or Iceland.

Where do students go to school for the fewest number of hours? Which families spend the most money on school supplies? And which country sees its students attend school for a whopping 23-year average?

Here are some of our favourite facts from education systems around the globe.

How much paper and glue can $27.5bn (£21.5bn) buy?

In the US, the average family now spends about $685 (£537) on their child’s back-to-school necessities from kindergarten to secondary school, an increase of nearly $250 (£196) since 2005 – and that works out to $27.5 billion (£21.5bn) total for the 2018 schoolyear.

Combined with university spending, the number climbs to $83bn (£65bn). The most expensive items are computers at an average spend of $299 (£234) per household. Clothing is close behind at $286 (£224), followed by electronics like tablets and calculators at $271 (£212). Last are the basics: binders, folders, books, highlighters and the rest, which cost $112 (£88). The amount spent on school supplies is on track to continue rising through 2018 and beyond. (Source: Statista / Deloitte)

Danes spend 200 hours a year more in school than the average student.

Of 33 developed nations, primary students in Russia have the fewest required instructional hours per year – just over 500 (the international average is 800 hours). This translates to about five hours a day, with breaks between each class, during an eight-month-long schoolyear. But that doesn’t seem to be holding the country back too much: Russia’s universal literacy rate is almost 100%.

Then there is Denmark. The country requires primary school students to spend about 1,000 hours a year in class. That’s nearly two more months than Russia, and Denmark has longer schooldays. As a country consistently ranked in the top five for education, however, perhaps Denmark proves there are some benefits to having such a long school year. (Source: OECD)

Looking for a cheap education? Skip Hong Kong.

Depending on where their children go to school, a family could be looking at a difference of more than $100,000 (£78,000) in total costs. After combining class fees, books, transport and accommodation from primary up to undergraduate school, Hong Kong was found to be the most expensive place to go to school in the world — and by quite a margin. Parents in Hong Kong contribute an average of $131,161 (£102,750) out of their own pockets to a child’s schooling, after any scholarships, loans or state support.

The United Arab Emirates comes in second at about $99,000 (£78,000), followed by $71,000 (£56,000) in Singapore and $58,000 (£46,000) in the US. Despite the soaring cost of US universities, parents pay for just 23% of the yearly cost themselves on average. Compare these numbers with France, where parents only contribute about $16,000 (£12,500) to the entirety of their children’s education.  (Source: HSBC / Sallie Mae)

Parents aren’t the only ones who pay the price for school. Just think of the trees.

Even in the age of virtual reality, 3D printing and drones, the simple pencil continues to make a mark in institutions across the world. Today, more than 400 years after their invention, an estimated 15 to 20 billion pencils are produced each year.

Cedar trees found in the Pacific Northwest are the most common source of pencil wood in the US, while most of the graphite is mined in China and Sri Lanka. Approximately 60,000 to 80,000 trees are cut each year to maintain the world's pencil supply. (Source: The Economist)

Students in Australia attend class for a quarter of their lifetime.

At some point, school is meant to end. But in countries like New Zealand and Iceland, that isn’t for almost two decades. A student’s ‘school life expectancy’ is calculated by the average enrolment rates for different ages from primary school to the undergraduate university level. Australia currently holds the longest expectancy at 22.9 years from primary school to university, or from six years old to about 28. At the bottom of the list is Niger, where students generally begin primary school at the age of seven. Here, the average time a student spends in school is as few as 5.3 years – a 17-year difference. (Source: Global Innovation Index)

Join 900,000+ Future fans by liking us on Facebook, or follow us on Twitter or Instagram.

If you liked this story, sign up for the weekly bbc.com features newsletter, called “If You Only Read 6 Things This Week”. A handpicked selection of stories from BBC Future, Culture, Capital, and Travel, delivered to your inbox every Friday.