10 to 15 minute walk from Railway Station to Bus Station.
Then Harrogate bus 36 from Leeds Bus Station towards Harrogate and Ripon. Nearest bus stop to Leeds Grammar School is Alwoodley Gates, then a 10-15 minute walk.
The 36 bus runs every 10 to 15 minutes on Saturday (depending on the time of day) and every 30 minutes on Sunday.