Students are often unaware of time-how long it takes to do a task, time passage during tasks, etc.
Students are often unaware of how they compare with the rest of the class in doing and completeing work. You need to train and develop this sense. While students are doing independent work or during tests, constantly give the time in minutes. You have worked 40 minutes, there are 10 minutes to go. You took 45 seconds to get ready- that is too long.