Municipality	Type of municipality	Language used at home
		% Catalan	% Spanish	% Catalan and Spanish	% other	Total
A	Catalan-speaking municipalities	59,7	16,2	12,4	11,7	100
B		56,2	9,5	5,5	28,8	100
C		45,6	11,9	20,7	21,8	100
D		43,4	29,6	29,9	6,1	100
E	Bilingual municipalities	35,9	35,8	20,2	8,1	100
F		35,4	32,7	21	10,9	100
G	Spanish-speaking municipalities	16,6	59,2	14	10,2	100
H		13,6	61,7	20,3	4,4	100
I		11,7	61,5	25,7	1,1	100

2. Intensity of linguistic segregation and incidence of residential segregation

As we shall see below, the key variable throughout our analysis is the percentage of pupils who use Catalan at home, whether exclusively or together with other languages (mainly Spanish). The reason for prioritising this category lies in the supposition that these pupils have a high degree of familiarity with the Catalan language, which can favour its informal use among peers. We have, therefore, opted to consider as a group those cases in which Catalan is present in the child's home background, allowing for the fact that he/she may be familiar with the use of other languages. When we use the category Catalan-speaking pupils, we shall henceforth be referring to those cases in which Catalan is used in the home, whether or not it is used exclusively.

The classification of municipalities given above shows the first factor in linguistic segregation in the Catalan school system: the differences between municipalities regarding the proportion of pupils who speak Catalan at home. As is logical, the proportion of pupils with this profile that we find in each school clearly depends on the number in the whole municipality. Of the categories referred to (Catalan-speaking, bilingual and Spanish-speaking municipalities) the first two have average numbers using Catalan at home in excess of 50%. The average is 65.7% for Catalan-speaking municipalities and 56.2% in bilingual municipalities, whereas in Spanish-speaking municipalities the average is considerably lower, at 31.4%. This distribution of pupils shows how Catalan is a minority language in the third type of municipality. In such municipalities, if Catalan-speaking pupils were evenly distributed, they would constitute a minority of the pupils in all schools, while, if the distribution is highly segregated, Catalan-speaking pupils will tend to concentrate in a minority of schools where there is a Catalan-speaking majority, a situation which does occur in some cases, as we shall see.

We can thus see that the observation of Albert Bastardas regarding the influence of residential segregation on linguistic segregation in Catalonia is substantially correct: "The residential concentration and resulting quasi-segregation of many Spanish-speaking individuals in Catalonia is a characteristic feature of the Catalan situation. The demo-linguistic composition of schools in Catalan metropolitan areas logically reproduces that of society in general, and that of the district or area in particular" (Bastardas, 2002:5). There is certainly a linguistic segregation associated with residential segregation -both between and within municipalities- which has a notable effect on the linguistic make-up of schools. However, as we shall see, language segregation in the school system is not explained only by residential segregation.

To appreciate the intensity of linguistic segregation in schools we will start by using indices of segregation. These indices range from 0 (a situation in which we find no segregation, which means that the distribution of the sub-group studied is proportional to the distribution for all the schools in the universe) and 1 (maximum segregation possible, which means a distribution of the sub-group of population which is as disproportionate as possible, concentrating all the members of the sub-group in the smallest possible number of schools). It should be pointed out that the index of segregation is an eminently comparative measurement, which serves above all to compare the intensity of the phenomenon in different municipalities. The table below shows some indices of linguistic and social segregation (as mentioned above, by social segregation we mean segregation stemming from differences in the parents' level of education) in different municipalities:

Table 2. Indices of segregation in schools by municipality according to language and educational background

Municipalities	Indices of segregation in schools
	Language segregation			Social segregation
	Catalan speakers	Spanish speakers	Other languages	Compulsory education or less	Higher studies
A	0,38	0,19	0,51	0,41	0,24
B	0,2	0,28	0,19	0,29	0,36
C	0,53	0,4	0,53	0,35	0,69
D	0,3	0,31	0,2	0,22	0,26
E	0,39	0,28	0,63	0,31	0,34
F	0,39	0,43	0,35	0,36	0,18
G	0,56	0,38	0,59	0,47	0,24
H	0,24	0,19	0,48	0,21	0,15
I	0,1	0,1	0,79	0,24	0,3