My son quit his drawing class the same week his little sister joined it

Two years he has gone to this class on Saturdays. He liked it. Last week his sister, who's three years younger, asked to join, and the teacher put her in the same batch because the timing suited us. He went once with her and now says drawing is 'boring'. I know exactly what this is. So does he. What I don't know is whether to make him go back, find him a different batch, or let him drop it and see if he misses it. We're in Adyar, if anyone knows another weekend art class for a 12 year old.