Source B
"It was mandated that the locals attend the newly-erected Japanese schools, and learn the language. Existing schools were pressured to teach their curriculum in Japanese, and students were made to sing the Japanese national anthem. However, there was a lack of Japanese teachers and textbooks, and the Japanese were forced to allow a combination of the Japanese and English languages until the arrival of the first Japanese textbook in Singapore. To further supplement Japanese education, Japanese lessons were played over the schools" broadcasting systems
_{(this part is sourced from the Singaporean history textbook Singapore: From Settlement To Nation Pre 1819 To 1971).}

From the both sources,I can infer that the lives of teenagers were probably having difficulties coping with their studies back then. Source A shows that there were British people wearing uniforms and this tells me that all of them could be attending an English school as there were no other races around hence, before the Japanese Occupation, people went to different schools depending their language and races.
However, as seen from source B, during the Japanese Occupation, students were forced to join newly-erected Japanese schools and learn the language. Schools were forced to teach their lessons in the foreign language and students were required to sing the Japanese national anthem for flag-raising. Some teenagers were forced to withdraw from their existing schools to join the Japanese ones. Thus, based on the souces given above, I can infer that the lives of the teenagers were probably having difficulties coping with their subjects back then. 

Source B

https://battleofsingapore.wikispaces.com/The+Japanese+Occupation

Based on the three sources,I can see that the teenagers' lives were affected as there was not enough food for them .In source A, there were people crowding at the street centre, enjoying their food and this shows that the problem shortage of food did not occur back then and people were not fretting over without having enough food to it However, during the Japanese Occupation, shortage of food occur and people were given ration cards to collect their food as seen from source B and source C,there were a limited amount of food for the locals and thus, there were some days where people had no food to eat. Sometimes, locals would have to resort to eating porridge for weeks or months.Also,due to the cramped and unsanitary conditions and lack of food, many locals and POWs contracted illnesses like malaria, cholera and suffered from malnutrition. Since there was little medication to treat the patients, many were dead. This shows how Japanese were heartless and inhumane and spared no thoughts for the locals living in Singapore at that time. Hence, I can infer that the lives of teenagers were affected by this as it means that there was not enough food for them.