Harbor City school officials this week rolled out a districtwide measurement style guide after a middle school science lab misreported caffeine content by three orders of magnitude — an error traced not to math, but to how students wrote their units.

The mistake surfaced during what was supposed to be an easy comparison: students in the district’s after-school “Everyday Chemistry” club tested beverages for caffeine and recorded results on a shared spreadsheet.

One group entered “0.18 g” for a 12-ounce soda sample. Another group, using the same test strip kit and a different drink, recorded “180 mg.” The two values were meant to match.

“Everyone argued for 10 minutes about which drink ‘had more caffeine,’ and the problem was the units, not the science,” said club adviser Naila Soren, who teaches at Bayview Middle School. “The kids weren’t wrong — the writing was.”

Superintendent Elias Porter said the incident prompted a broader review of how units are introduced, written and compared across classes — from science labs to computer clubs to personal finance electives.

“We realized students were learning the words, but not the habits,” Porter said. “The habit is what prevents mistakes.”

The poster that started it: Base units and prefixes

On Monday, the district began hanging new “Measurement Matters” posters in classrooms and labs. The poster’s top line reads: “Write what you measured, with the unit, every time.”

It then lists SI base units students see most often in the district:

• meter (m) for length
• second (s) for time
• kilogram (kg) for mass
• liter (L) for volume (used alongside SI in class activities)
• pascal (Pa) for pressure (introduced in earth science)

Under that, in bold, it lists common metric prefixes and their symbols — the part Soren says tends to blur in students’ memories:

• kilo (k) = 1,000
• centi (c) = 1/100
• milli (m) = 1/1,000
• micro (µ) = 1/1,000,000

“It’s not that they can’t do the conversion,” Soren said. “It’s that they don’t choose the unit that makes the number understandable at a glance.”

Choosing magnitudes that make sense

The district’s guide emphasizes selecting a unit that keeps the number in a readable range — often between about 1 and 1,000 — so comparisons are easier.

At Bayview’s lab tables this week, the same caffeine data was rewritten in a consistent form:

• A coffee sample recorded as 0.095 g became 95 mg.
• A soda sample recorded as 180 mg stayed 180 mg.

“Seeing 95 and 180 next to each other is instantly comparable,” said eighth grader Jordan Lee. “Seeing 0.095 and 180 is like, wait, what?”

Computer science teacher Alina Mercado said the same idea shows up in the district’s gaming and robotics clubs when students talk about internet response times.

“If your ping is 0.045 s, that’s true, but nobody talks like that,” Mercado said. “Students understand 45 ms right away, and they can compare it to 120 ms without a calculator.”

In earth science, the guide encourages using kPa rather than Pa for everyday atmospheric pressure.

“Writing 101,000 Pa is correct, but it’s not friendly,” said teacher Owen Bhatia. “101 kPa is the same measurement and it looks like what you’d see on a weather map.”

Correct symbols, spacing — and what not to do

The style guide also addresses formatting that teachers say routinely causes confusion.

In a ninth-grade lab at Harbor City High School, chemistry teacher Dana Rutledge circled a student’s notation in red: “75MG.”

“The symbol is mg, not MG,” Rutledge told the class. “Capital letters mean different things.” She pointed to another paper: “And it’s mL, not ml.”

Rutledge asked students to rewrite several entries using the guide’s conventions:

• Put a space between the number and unit: 250 mL, not 250mL.
• Don’t pluralize symbols: 5 mL, not 5 mLs.
• Avoid periods after symbols: 10 s, not 10 s.
• Use correct capitalization: ms (milliseconds), m (meters), kPa (kilopascals), L (liters).

“Kids see adults type ‘lbs’ and ‘oz’ and think it’s all flexible,” Rutledge said. “In science and engineering, the symbols are part of the measurement.”

Reading scale increments: Small marks matter

To address another common source of errors — misreading tick marks on rulers, thermometers and gauges — the district’s materials include simple text examples that teachers can reproduce on the board.

In one classroom, Bhatia drew a thermometer scale in marker and asked students to report the temperature. The key was recognizing what each tick represented.

Thermometer example (each small tick = 1 °C):

The caret sat on the third small tick after 20. Several students initially answered “23,” then corrected themselves after counting: 23 °C.

“That exercise isn’t about temperature,” Bhatia said afterward. “It’s about the habit of identifying the increment before reading the value.”

In a separate lesson, Rutledge used a ruler-style scale to reinforce the same idea.

Ruler example (each small tick = 1 mm):

The caret landed on the eighth small tick after 10, meaning 18 mm. When a student wrote “1.8 cm,” Rutledge accepted it as equivalent — then asked which was more convenient for the class’s comparison table.

“Because most of our measurements were between 12 and 28, mm kept everything in the same unit and made the table easy to scan,” she said.

Everyday numbers: caffeine, hydration and the “unit-like” percent

The district’s guide leans into examples students say they actually care about.

In the cafeteria, a poster near the vending machines lists typical caffeine amounts in mg — not because grams are wrong, but because milligrams match what labels and nutrition databases use.

“It’s how the world talks about caffeine,” said school nurse Priya Desmond. “If a student reads a label that says 160 mg, we want them to recognize that number and not confuse it with 160 g, which would be absurd.”

On hydration, the guide suggests tracking water intake in mL for a bottle and L for a day.

“A student might drink a 500 mL bottle at lunch and think in bottles,” Desmond said. “But for daily intake, 2 L is a simple number to remember and compare.”

In personal finance class, teachers said a different symbol causes trouble: the percent sign.

“Percent isn’t an SI unit, but it behaves like one in a spreadsheet,” said economics teacher Leonard Cho, who assigns mock portfolios. “If you forget the percent sign, you change the meaning.”

Cho pointed to a recent assignment in which a student wrote “Return: 0.07” in one row and “Return: 7%” in another.

“Those can represent the same thing, but only if you’re consistent about the format,” Cho said. “Writing 7% makes it explicit. It’s a unit-like label: it tells you the scale is ‘per hundred.’”

Cho’s class now records returns as % and fees as % as well, while recording dollar amounts with $ and time horizons in years (yr) or months (mo), depending on the comparison.

What changed after the caffeine lab

The district is not banning any units, Porter said. Instead, the new guide asks teachers to require three steps whenever students record a measurement: write the value, write the unit correctly, and choose a magnitude that helps others read and compare.

On Friday, Soren’s club repeated its beverage test. The debate ended quickly.

“The numbers finally spoke for themselves,” said eighth grader Lee, looking at a neatly formatted table. “When everything is in mg, you can just tell.”

Checklist: Recording a measurement correctly

• What is the quantity? (mass, time, volume, pressure, return)
• What unit symbol will you use? (mg, ms, mL, L, kPa, %)
• Is the symbol correctly written? (case matters: mL not ml; ms not MS)
• Is there a space between number and unit? (250 mL, 45 ms)
• Is the magnitude convenient for comparison? (use mg vs g, ms vs s, kPa vs Pa)
• Did you confirm the scale increment before reading? (identify what each tick mark represents)
• Did you keep units consistent across the table/graph? (don’t mix mg and g without converting)
• If using percent, did you include % and keep the format consistent? (e.g., 7%)