Score Keeper

Hook 5 min

1. "Think of the scoreboard at a basketball game. What numbers are on it?" (The score, the time, the period.)
2. "Which of those change during the game? Is there one that stays the same?" (Score and time change. How long a period lasts stays the same.)
3. "Something tells a scoreboard to change. Let's watch a game's program keep its numbers, and catch what changes them."

Explore 17 min

1. On the projector, point to the five boxes under the game: score, lives, speed, best, goal. "Each box is a variable: a name and one value inside."
2. Press Play. A student steers with the arrow buttons. At the first star the game freezes, when you catch a star: lights up, then score = score + 1, and a new number flies into the score box. Stop: "Score was 0. Now it's 1. Where did the 0 go?" (It's gone. A box holds one value at a time.)
3. Press Pause, then Step a few times. Before each press: "Which box will change on this line?"
4. When 10 seconds pass and speed goes up: "Who pressed something to change speed?" (Nobody. Time passing changed it.)
5. At Game over, before pressing Play again: "Which boxes will start over? Which will keep their number?" Then press it and check. (Score, lives and speed start over. Best and goal keep theirs.)
6. Pairs open Lab. Autopilot and Same sky are on, so every run is the same until you turn a dial. For each question: read the question card and do what it says, press Run, then Save to notebook on the result card, then Next ▶. Switch Code speed to Quick after the first run to save time.
7. Every pair does questions 1, 2, 3 and 6. Fast pairs do all seven.
8. Stop the class after question 3: "The rock line still ran. Which box stopped changing?" (Lives. The line ran, but the value stayed the same.)

Make sense 10 min

1. Pairs open Notebook. They put each card in Stayed the same or Changed, using the Same and Changed buttons, then press Check with my runs. If a card says Look again, move it and check again.
2. Whole class: "Which variable never changed in any run? How do you know?" (Goal. Its card says it changed 0 times.)
3. Fill the board chart together: score (catching a star), lives (a rock hit), speed (10 seconds of time), best (a game ends with a higher score), goal (nothing).
4. "Best changed only once or twice. Is it stored or changing?" (Changing, just not often. It keeps its value from game to game.)
5. Read the line under the bins aloud: a variable is a named box that holds one value.

Apply 8 min

1. Pairs pick a real game: tag, a board game, jump rope or the class points jar.
2. On paper they list three variables it would need, each with a starting value and what changes it, or "stays the same". Example: "points = 0, changes when the class is on task."
3. Two pairs share: "Stored, or changing? What changes it?"

Exit check 5 min

On a slip, each student answers: "A jump rope program has three boxes: jumps, time left and rope color. Circle the one that stays the same. For each other one, write what changes it." (Rope color stays the same. Jumps changes when you jump. Time left changes as time passes.)