@Oratory1 yes, really 5 minimum. They don't all have to be on school days though, but they have to do them before the summer.
I haven't been through it yet, but I am guessing that the school encourages each student to have absolute clarity about what they are aiming for by the first day of year 13.
That way the school can group them together, as appropriate and optimise towards meeting their goals e.g.. prepare for MAT or STEP and get those applications and personal statements done and submitted in good time!