This year, just like last year, the nearly 200,000 kids in Chicago’s public elementary schools spent recess indoors during the first week of school, when the heat index hit 114 degrees. In the past few weeks, outdoor activities were canceled at schools in and around Washington, D.C., where temperatures exceeded 100 degrees last month, and in Southern California too. These schools have good reason to exercise caution: Kids are particularly susceptible to extreme heat, and in a tragic incident last year, a 12-year-old in California collapsed during P.E. and died on day two of an excessive-heat warning. A bill named after him—Yahushua’s Law—is currently on the governor’s desk and would require the state to set temperature standards for outdoor school activities, including recess. As the first and last weeks of school keep getting hotter in some places, recess might be moved indoors day after day. But kids also need to be outside: Recess can improve grades and is where kids learn how to problem-solve and cooperate. The quickest way to keep playgrounds open through extreme …