To provide a precise answer about the duration of the obligatory lower secondary school program in the canton, I would need to know which specific canton you're referring to, as Switzerland comprises multiple cantons, each potentially having different educational systems and regulations.

However, generally in Switzerland, the lower secondary school program typically lasts for three years. This phase typically includes the final years of compulsory education following primary school and prepares students for further education or vocational training.

If you have a specific canton in mind, please let me know, and I can provide more detailed information.