The cantons and their municipalities are responsible for the organisation and financing of the lower secondary level. The municipalities (and, in some cantons, the cantons as well) are responsible for the establishment and maintenance of pre-schools. School attendance is compulsory and free of charge.

The lower secondary level follows the primary level and lasts 3 years (school years 7 to 9). In a few cantons, the lower secondary level begins earlier and lasts 5 (beginning in school year 5) or 4 years (beginning school year 6). The harmonisation of compulsory education (HarmoS) will standardise the school structures in the cantons which join the HarmoS Concordat.
The lower secondary level provides basic general education and preparation for basic vocational education and training or for transfer to schools providing a general education on the upper secondary level. Pupils at the lower secondary level are generally between 12 and 15 years of age.

At the lower secondary level, teaching is realised on the basis of different models at different performance levels. Depending on the canton, either a single model is implemented throughout the entire canton, or the canton allows the municipalities to choose between various models (model diversity):

Separated model
Pupils are allocated to institutionally separate school types, according to their performance levels. The structure is based on the principle of equal capacities among pupils. Generally, each school type has its own adapted curricula, teaching material, teachers and, in some cases, its own range of subjects. In general, there are 2 to 3 school types (4 in a minority of cantons), the names of which vary. In the structure with 2 school types, a distinction is made between the performance-based group at basic level (with the least demanding requirements), and the performance-based group at advanced level. In the structure with 3 school types, there is a performance-based group at basic level, a performance-based group at intermediate level and a performance-based group at advanced level. The requirements of the performance-based group at advanced level are the most demanding and this school type generally prepares pupils for transfer to the matura schools.

Cooperative model
The cooperative model is based on core classes with different performance requirements. Each pupil is assigned to a core class according to his or her performance level. The pupils attend lessons in certain subjects in differentiated requirement-based groups (whereby the core classes are mixed).

Integrated model
The integrated model does not use different school types or core classes. Pupils with different performance levels attend the same class and mixing is maintained. In certain subjects, teaching occurs on differentiated requirement-based levels.

The separated model entails low permeability. The cooperative and integrated models enable a high degree of permeability. The separated model predominates. The vast majority of cantons have schools according to this model and the variant with 3 performance-based groups is the most widespread. In around half of the cantons, the separated model coexists alongside the integrated or cooperative model. Only a few cantons adhere exclusively to the integrated and / or cooperative model.