Presentation: Screen Time and Sleep

Slide 1 of 7 · Settling starter · PSE / Well-being · Year 9

3 minutes

Screen time and sleep: one pupil’s 2-week experiment

You have a worksheet with Lowri’s sleep diary printed on it. Lowri is an invented Year 9 pupil in Wrexham. In Week 1 her phone stayed in her bedroom all night. In Week 2 she charged it in the kitchen from 21:30 and used an old alarm clock. Today you work out how much she slept, compare the 2 weeks, draw the results, and decide how much her experiment really proves.

While the register is called: write your name, class and date on your worksheet, then read the box What the experts say.

Starter question: How many hours a night do the NHS sleep experts say most teenagers need, and what is the warning level?

DCF: Citizenship → Health and well-being No computers needed · calculator and ruler · Lowri is invented

Supply teacher script (no subject knowledge needed)

Hand out: one worksheet per pupil, plus a calculator, a ruler and a pencil each. No computers or phones are needed; the diary is printed on the worksheet. If you are in a computer room, the same data is in the file sleep-diary-two-weeks.csv (the Stimulus link above) and pupils may use =AVERAGE() in a spreadsheet for Step 2. Lowri is invented; nobody has to talk about their own sleep, and Step 5 is private. Safeguarding: if a pupil says they cannot sleep because of worry, something at home, or messages at night, do not discuss it in front of the class. Say “come and see me at the end”, take their name, and pass it to the class teacher or the safeguarding lead the same day.

Say aloud: “Name, class and date at the top. While I take the register, read the box called What the experts say. Find 2 numbers: how many hours most teenagers need, and the level below which you are probably not getting enough.”

Starter answer: most teenagers need 9 to 9.5 hours a night; the normal range is 7 to 11 hours, and getting less than 7 hours most nights probably means you are not getting enough. Also on the sheet: most people fall asleep within about 30 minutes, stop using your phone at least an hour before bed, charge it anywhere but your bedroom, and the Chief Medical Officers say “Leave phones outside the bedroom when it is bedtime.”

Slide 2 of 7 · Today’s brief and key words · PSE / Well-being · Year 9

3 minutes

Your brief: calculate, compare, chart, then ask what it proves

You will work out hours asleep and minutes to fall asleep for all 14 nights, fill the comparison table with school-night averages, draw a paired bar chart with a 7-hour line, answer 4 questions about what the data shows and cannot prove, and privately plan a fair test of your own.

Across midnight

From 23:45 to 07:00 is 15 minutes to midnight plus 7 hours. Write hours as a decimal: 7 h 15 min = 7.25.

School nights

Sunday to Thursday, the 5 nights before a school day. Average school nights with school nights, and weekends with weekends.

Link, not proof

A link means 2 things change together. Proof means 1 causes the other. The Chief Medical Officers say screens research shows a link, not proof.

DCF: Citizenship → Health and well-being Quote figures with their units · compare like with like

Slide 3 of 7 · Step 1: Lowri’s diary · PSE / Well-being · Year 9

11 minutes

Step 1: hours asleep and minutes to fall asleep for all 14 nights

For each night fill the 2 empty columns: hours asleep (from “fell asleep” to “woke up”, as a decimal) and minutes from lights out to asleep. Week 1 Sunday is on the board: copy it, then do the other 13 nights.

Night	Lights out	Fell asleep	Woke up	Hours asleep	Minutes from lights out to asleep
Week 1 Sunday	22:30	00:00	07:00	7 h = 7	22:30 → 00:00 = 90

Step 1 on your worksheet · 11 minutes, on your own Count to midnight first, then add the hours after it

Slide 4 of 7 · Steps 2 and 3: compare, then draw · PSE / Well-being · Year 9

14 minutes

Step 2 & Step 3: the comparison table, then the paired bar chart

Step 2 (6 min): fill the 5 rows of the comparison table. School nights are Sunday to Thursday. Row 1 is on the board: copy it and show your totals. Step 3 (8 min): draw 2 bars per night, Week 1 shaded and Week 2 white, from zero. Draw a dashed line across at 7 hours and label it. Add a title and a key.

Measure	Week 1	Week 2	Difference
Average hours asleep on school nights	35.5 ÷ 5 = 7.1	40.5 ÷ 5 = 8.1	+1.0 hour a night

Steps 2 and 3 on your worksheet · 14 minutes Bars start at zero · key, title and the 7-hour line

Supply teacher script (no subject knowledge needed)

Say aloud: “Row 1 is on the board: add the 5 school-night hours, divide by 5. Copy it, then do the other 4 rows, showing the total before you divide. Then the chart: ruler and pencil, 2 bars for each night side by side, Week 1 shaded, Week 2 left white, bars from zero, dashed line at 7 hours, a title and a key.” In a computer room pupils may use =AVERAGE() over the 5 school nights instead.

Quick check, Step 2: Friday and Saturday average: 18 ÷ 2 = 9.0 and 18.5 ÷ 2 = 9.25, +0.25 hours. Minutes to fall asleep on school nights: 420 ÷ 5 = 84 and 120 ÷ 5 = 24, 60 minutes quicker. Times woken by phone, all 7 nights: 6 and 0, 6 fewer. Average energy after school nights: 10 ÷ 5 = 2.0 and 18 ÷ 5 = 3.6, +1.6 points.

Walk the room, Step 3: a secure chart has bars starting at zero, a title such as “Lowri’s hours asleep: phone in bedroom vs phone in kitchen”, a key showing shaded = Week 1 and white = Week 2, and a labelled dashed line at 7 hours. Only 1 bar should fall below that line: Week 1 Wednesday at 6.5.

Slide 5 of 7 · Steps 4 and 5: what it shows, then your own test · PSE / Well-being · Year 9

14 minutes

Step 4 & Step 5: what the data shows and cannot prove, then plan privately

Step 4 (9 min): answer (a) to (d) in full sentences, quoting figures with units. For (d), Lowri says “This proves phones ruin sleep.” Give 3 different reasons why her diary cannot prove that on its own. Step 5 (5 min, private): plan a 1-week experiment you could try yourself. Nobody will ask to see it.

Question	Model answer
(a) Which difference is the biggest? Quote both figures.	How long she took to fall asleep on school nights: 84 minutes in Week 1 and 24 minutes in Week 2, an hour quicker. In Week 2 she was inside the “about 30 minutes” the experts call normal.

Steps 4 and 5 on your worksheet · 14 minutes Use the notes column as evidence · Step 5 stays private

Supply teacher script (no subject knowledge needed)

Say aloud: “(a) is on the board as a model. Write (b), (c) and (d) in full sentences with figures and units. For (d), look at the notes column and at how the data was collected. Then Step 5, on your own and private: the one thing you would change, what you would record, what you would keep the same, and what result would tell you it worked. I will not ask anyone to share it.”

Quick check: (b) Week 1 school-night average 7.1 hours is only just above the 7-hour warning level and well short of 9 to 9.5. On Wednesday of Week 1 she slept only 6.5 hours; the note says a group chat went on late and she last looked at her phone at 00:15. Week 2 average 8.1 hours, no night below 7.75; still under 9, so it helped but did not solve everything. (c) Week 1 she woke at 09:45 and 10:30, which is 2 hours 45 minutes and 3 hours 30 minutes later than 07:00; Week 2 08:30 and 08:45, only 1 hour 30 minutes and 1 hour 45 minutes later. A long lie-in means fewer hours awake by bedtime and moves the body clock later, like jet lag, so she is not sleepy at 22:30 the next night. (d) three different kinds of reason: (1) one person for 2 weeks, 7 nights each, is not enough to rule out chance; (2) other things changed too: a late group chat and a film in bed in Week 1, and in Week 2 she was worried about a maths test on Thursday and still slept worst that night, so sleep depends on more than the phone; (3) the times are her own estimates and the energy scores her own opinion, and she knew what she was testing, so she may have expected Week 2 to feel better. It fits the advice but does not prove it.

Walk the room, Step 5: do not read anyone’s Step 5. A secure plan changes 1 thing (for example no screens after 21:30 on school nights), records the same things every night, keeps everything else normal, and decides in advance what result counts as working.

Slide 6 of 7 · Self and partner check · PSE / Well-being · Year 9

2 minutes

Swap with your partner and check Steps 1 to 4 against the success criteria

Fold Step 5 under before you swap. Tick each success criterion your partner’s work meets. Then swap back and correct 1 thing: a night that crosses midnight, or a figure with no unit.

I can calculate time asleep across midnight and find averages that compare like with like, school nights with school nights.
I can draw a paired bar chart starting from zero, with a key, a title and a reference line.
I can compare real data with expert guidance and quote figures with their units.
I can explain why one person’s 2-week diary shows a link but does not prove a cause, using details from the data.
I can plan a fair test of my own habits, saying what I will change, record and keep the same.

2 minutes · partner check, Step 5 folded under Finished early? Extra school-night sleep in Week 2, over a 38-week school year?

Supply teacher script (no subject knowledge needed)

Say aloud: “Fold Step 5 under so it stays private. Swap. Tick the criteria your partner has met. Check Week 1 Wednesday: 6.5 hours and 120 minutes. Check the 7-hour line is drawn and labelled. Swap back and fix 1 thing.”

Extension answers: across the 5 school nights she slept 40.5 − 35.5 = 5 extra hours in Week 2; over 38 school weeks that is 5 × 38 = 190 extra hours. Thursday of Week 2 (7.75 hours, 45 minutes to fall asleep, worry about a maths test) shows that worry affects sleep even without a phone, so sleep depends on more than one thing. A good text is under 30 words and friendly, for example: “Phone goes in the kitchen at half nine now, so I will not see anything till morning. Not ignoring you, just sleeping. Catch up at school.”

Slide 7 of 7 · Plenary review · PSE / Well-being · Year 9

3 minutes

Round the room, then quick-check answers before handing in

Everyone names 1 figure from the comparison table with its unit, nobody repeats one. Then check these answers.

Question	Correct answer
What were Lowri’s school-night averages for hours asleep?	7.1 hours in Week 1 and 8.1 hours in Week 2: 1 extra hour a night with the phone in the kitchen.
How many times was she woken by her phone in each week?	6 in Week 1 and 0 in Week 2.
Does the diary prove that phones ruin sleep?	No. One person, 2 weeks, other things changed too (a late group chat, a test worry), and the times are her own estimates. It shows a link, not a cause.

Check your name and class are on your worksheet Worksheets in, face down · rulers and calculators back to the front