Could always use the unofficial swimming facility, the river lea! Trouble was you had to cross the main line to get to it.
This is not quite acurate as you could go under the railway line and we did this often when taking walks to the chestnut woods on the other side of the Lee.
Coming out of Highbury, one turns right taking the road past the sanitorium and then on to the farm and continue down the path towards the Lee. How we got across to the other bank I cannot remember. Some bright spark will remember.
Dave, if you have Google Earth just take a look at the old school and grounds as little has changed.
So dont get wet and buy some modern swimming trunks not those old wooly ones.
Shelaghe, there was a tennis court which was behind the nursery school to the left going towads the boys woods. Out of bounds to us and the only person I ever saw playing there was Shutt and his friends.