Long Residency

Recently I have received an email for my application as they need evidence for my long residency. I am aged 18 years and have lived in the UK for at least half
of my life. They asked me to send acceptable evidence for my long residency which includes “Letters from college or school – must be dated/signed and state attended from and to dates”. Can I ask my secondary school to write a letter confirming my attendance between 2016-2021? Will that cover those years? I’ve got evidence before 2016 and after 2021.