Whether for school or work, you can always find a good use for a backpack. Maybe not a good choice if you prefer lots of colour choices, but it does come in black.
From Nike
Nike Sportswear Futura 365 Women's Mini Backpack (6L) - Black - Polyester - ONE SIZE
House of Fraser
Nike Sportswear Futura 365 Women's Mini Backpack (6L) - Black