This study is pertinent to the field of teaching of French as a Foreign Language. It deals with the sequential writing of the students at the beginning of their learning of this particular language. The objective of the study was to check the importance of the sequential mistakes in the writing; to highlight the different types of these sequential mistakes that students commit and to assess the influence of the student's age on committing such sequential mistakes. To achieve the goals of the study, we performed both qualitative and quantitative types of analyses for the writings of the three groups of students. The first group consisted of 40 students (enrolled in the third year of the primary school), the second group consisted of 40 students (enrolled in the first year of the preparatory school) and the third group consisted of 40 students (enrolled in the first year of the secondary school). The analysis of the writings of the three groups revealed that 75.83 % of the students were inflicted by the sequential mistakes, and 10.8 % of their writings carried these mistakes. In addition, the analysis of the writings revealed four types of sequential mistakes including mistakes of the units intrasyllables, the permutations of the syllables, the multigrammatical mistakes and morphemic mistakes. Also, our study revealed that the age of the students had an important impact on the student's number who committed the mistakes and on the rate of committing these mistakes. We observed that 62.50% of the students of the primary school committed 4.78 % of their writings as sequential mistakes; 62.50 % of the students of the preparatory schools committed 4.97 % of their writings as sequential mistakes and 87.50 % of students of the secondary schools committed 14.59 % of their writings as sequential mistakes. The increasing age of the student was associated with decreased ability to avoid committing the sequential mistakes (negative/inverse correlation). Taken as a whole our current study recommends starting the teaching of the French language at an early young age as possible, and this would improve the learning of this language.