Put the words into the gaps: 1. He'll a classroom with 15 or 20 students in it. 2. I think some things never change so when he is 12 years old what I don't want him to do, which is exactly what I did so those things might be different, like I would probably hang out with my friends and go skateboarding. 3. He'll a jet board instead.

1. The missing word in the first sentence is "have". The correct sentence should be: "He'll have a classroom with 15 or 20 students in it."

Explanation: The phrase "He'll" is a contraction for "He will," indicating a future action. The verb that should follow is "have," indicating possession or ownership of a classroom with a certain number of students.

2. The missing word in the second sentence is "not." The correct sentence should be: "I think some things never change, so when he is 12 years old what I don't want him to do, which is exactly what I did, so those things might be different, like I would probably hang out with my friends and go skateboarding."

Explanation: The word "not" is missing after the word "do." This change adds emphasis to the speaker's desire for the person not to do the same things they did when they were 12 years old.

3. The missing word in the third sentence is "have." The correct sentence should be: "He'll have a jet board instead."

Explanation: The word "have" is missing after the verb "He'll." The sentence suggests that instead of certain things being different, the person will possess or own a jet board instead.