Make sure you give your kids enough time and space for them to learn. Make sure kids practice reading and writing every day. Don't let them miss a day for anything. Sit on them, but not too hard. Make sure there's a World Book Encyclopedia in the house.
Any year is okay.
Buy it used. When they get home, give them the time and space to look at walls. If you treat kids like animals, they act like animals. Kids are kids. Don't forget it.