Aguero was selected for the Argentina U17 team to participate at the 2004 U-16 South American Championship in Paraguay in September. He participated in all of Argentina's group stage matches, scoring in a 2-1 win against the United States and a 3-1 win against Ecuador to help Argentina finish top of their group. Aguero scored in the 47th minute of Argentina's 1-0 quarter-final victory against Peru, setting up a semi-final match against Colombia which Argentina lost 2-0.  Aguero represented Argentina at two FIFA World Youth Championships, winning back-to-back world titles. He was part of the team that won the 2005 edition in the Netherlands, alongside his future 2008 Olympics squad teammates Fernando Gago and Lionel Messi. At the 2007 FIFA U-20 World Cup, held in Canada, Aguero scored twice and helped set up three goals in a 6-0 win over Panama in the second game of the group stage of the tournament. He then scored the only goal in Argentina's third match against North Korea from a free kick. Having qualified to the round of 16, he scored two of the three goals against Poland that would eventually give them a 3-1 win to advance to the next round. Argentina defeated Mexico in the quarter-finals and Chile in the semi-finals, and faced the Czech Republic in the finals, a team they drew 0-0 in the group stage. Aguero captained and scored the equaliser in the 62nd minute, leading to a 2-1 victory. In addition, Aguero won the Golden Boot of the tournament, scoring six goals in seven, and the Golden Ball as the best player of the tournament.  As a member of the Argentine squad for the 2008 Beijing Olympics, Aguero scored two goals in the space of five minutes in the semi-final 3-0 win over Brazil on 19 August 2008. Argentina went on to win its second consecutive gold medal at the Olympic tournament.

Answer this question "How did his team do during those championships?" by extracting the answer from the text above.
winning back-to-back world titles.