The COVID Social Mobility & Opportunities (COSMO) study is a new national cohort study generating high-quality evidence about how the COVID-19 pandemic has affected socio-economic inequalities in life chances, both in terms of short- and long-term effects on education, wellbeing, and career outcomes. A representative sample of young people in England who were in Year 11 in the 2021/2022 academic year were invited to take part in the survey, with the aim of following them as they progress through the final stages of education and into the labour market. This third brief finds that females, disadvantaged young people and state comprehensive pupils were more likely to change their education and career plans due to COVID-19. Young people who reported having had 'long COVID' or ill health, who were asked to shield or who experienced economic hardships were more likely to have changed their future plans. Disadvantaged students were less likely to receive information, advice and guidance (IAG) during the pandemic. This cohort of young people continues to have large inequalities in their educational aspirations. [For the first brief, "Lockdown Learning," see ED625712. For the second brief, "Education Recovery and Catch Up," see ED625714. For the fourth brief, "Mental Health and Wellbeing," see ED625716.]