This is indeed ‘where I learnt to swim’ , in the mid/late 60’s. Polystyrene ? float strapped to my back, and a no nonsense instructor. Also seem to remember swimming gala entries, i think maybe cubs rather than school, watching from the balconies above between events. However family moved to Bebington in 1972 ish and the new Oval sports centre made Byrne Avenue seem rather old. I am quite surprised it was ‘ only’ opened 1933…….as it was pretty ‘dated’ ‘only ‘ 30 years later. Would love to visit sometime.