The idea of longer school hours is going to widen the gap between those at good schools and those at struggling schools.
There will be some schools which offer a wide range of extra-curricular activities of a good quality. Other schools may only offer a very small number of activities, of less good quality.
I think children should be free to choose from a wide range of activities locally, whether it's chess, ballet, football, gymnastics, orchestra, French, Spanish, writing, computing, sailing, scouts, dance, drama, rugby, swimming, art, hiking, or any number of other things.
If a student is particularly interested, or talented, in one of the above, they should be able to pursue it with their local youth theatre, rugby club,, Spanish class, chess club, gymnastics team, youth orchestra etc. without having to stay at school doing something else. Then they can meet others with a similar level of interest/ability, which isn't something every school can offer for such a wide range of activities.