The degree of imbalance in access and participation is measured using gender gaps, which is the difference between the gross enrolment of males and the gross enrolment of females.

In Nigeria, gender gap of total enrolment in primary schools irrespective of age (Table 17) was 18.0% in 1993 and dropped to 10% in 1996. This drop could be attributed in part to the mobilisation and advocacy campaigns mounted by the Federal, State and Local Governments in collaboration with donor agencies, NGO;s and the media on girl-child education. It may also be accounted for by the drop in male enrolment during this period.

However, gender gaps are wide in some of the States. Benue state had an average gap of 66.5 in favour of boys from 1992-1996.

Attrition and completion rates at the primary and Junior Secondary School level will be discussed in absolute terms. School attendance records indicate a high degree of movement of children from one school to the other. When a child migrates from one town/state to the other as a result of one of the following:- natural disaster (flood, wind storm, and fire), communal clashes, transfer of working parents, creation of new local governments and boundary adjustment, it is difficult for the school to keep track of the pupils’ movement. The only available information is that the child has left that school. Adjudging from the situations within the location of the school it might also be that the child is still in the school system in the country. The causes of these migrations are sudden. Parents are in a hurry to move to their own states/local governments when new ones are created.

Another issue is the "second chance programme" which allows children who withdrew early from school for one reason or the other to be reabsorbed into the school system. The girl-child who drops out of school as a result of early marriage or pregnancy is encouraged to return to school after having her baby. Special schools have been opened for such children in States where high a degree of girl-child marriage has been identified.

As a result of constant migration in and out of the school system, attrition rates have been computed in absolute terms. The reconstructed cohort method could not be applied to the data from Nigeria to determine attrition rates and internal efficiency because of the various assumptions upon which the reconstructed cohort method is based.-

Assumption of homogeneous behaviour is not applicable to Nigeria for reasons given earlier.

Attrition rates have be calculated for example by expressing the difference between enrolment in primary one in year t and primary two in year t+1 a percentage of enrolment for primary one in year t. Primary one enrolment in Nigeria in 1990 was 3,077,149 and primary two enrolment in 1991 was 2,528,267. Thus the attrition rate from primary one to primary two in 1991 was:

(3077149 – 2528766)/ 3077149 x 100 = 13.8%

This is expressed in absolute terms but the value could be +ve or –ve depending on whether there were drop-outs or drop-ins. The strength of this method is based on the fact that incidence of repetition is very small at the primary school level.