Grade 6: Line Graphs

Warm up with a few quick line graphs warm-ups on the board while the class settles, so every child starts thinking about the skill.

A line graph shows how a measurement changes over time. Points are plotted for each reading, then joined with straight lines, so the slope shows whether the value is rising, falling or steady. Unlike a bar graph, a line graph is for continuous data (temperature through a day, plant height over weeks), where the values between the points have meaning. Model the method clearly, thinking aloud:

• Contrast it with a bar graph: use a line graph only when the horizontal axis is a continuous scale like time, so joining the points makes sense.
• Set up the axes: time along the bottom, the measured quantity up the side, with an even scale that fits the data.
• Plot each reading as a point at the right time and value, then join neighbouring points with straight line segments.
• Read the trend from the slope: rising line means increasing, falling means decreasing, flat means no change.
• Read between points (interpolate) with care, and ask when the value was highest, lowest, or changed fastest (the steepest part).

Work this through step by step on the board, then have the class talk you through a second one.

• Plant height over 4 weeks:
• week 1: 2 cm
• week 2: 5 cm (rose 3, steepest climb)
• week 3: 6 cm (rose 1, slowing)
• week 4: 6 cm (flat, no growth)

Do the first few questions of the practice worksheet together, one child explaining each step. Check for understanding before releasing the class to work alone.

Students complete the practice worksheet independently while you circulate and support.

Circulate and look for these, they are the usual sticking points:

• Using a line graph for separate categories that should be a bar graph.
• Plotting points but reading only the points, ignoring the trend the line shows.
• An uneven time scale on the bottom axis, which warps the slopes.
• Reading between points as if a value were certain when it was never measured.

Pull the class back together. Ask one child to explain line graphs in their own words, pose a single check question everyone answers on a mini whiteboard, and name what you will build on next lesson.

Use the independent worksheet as the evidence. A child who can complete it accurately and explain one answer has met the objective; anyone who cannot needs the easier level and a short reteach next session.