Worksheets
Here is a worksheet (factorising-quadratics-puzzle) I made that encourages lower-ability pupils to factorise quadratic expressions when a = 1. Each bracket that appears in the answers can be found in the answer bank, which the pupils have to cross off when each one has been used. There are more brackets than they need, which are highlighted on the teacher’s version of the answer bank.
Games
The excellent website Flashy Maths has a nice interactive game involving factorising quadratic expressions. A nice interface, and you can also download this to play offline for a bigger and better version.