interaction process between teacher and students: The labeling of students on the basis of relative characteristics, The

1 By means of the function of Lagrange (Klundert & De Groof, 1974) this point can be calculated.

2 All points beneath one (or beneath both) minimum levels) are equally unacceptable to the teacher. In that area no indifference curves can be drawn (see also Baumol, 1977 page 201, where a similar situation is stated, with the difference that in that case, only one good has a `minimum level').

REFERENCES

Ankersmit, T., Roelandt, Th. & Veenman, J. (1989). Minderheden in Nederland: Statistisch Vademecum 1989 [Minorities in the Netherlands: Statistical Handbook 1989]. 's Gravenhage: Staatsuitgeverij/ Centraal Bureau voor Statistiek.

Baumol, WJ. (1977). Economic theory and operations analysis. Englewood Cliffs, New York: PrenticeHall.

Beckerman, T. M. & Good, T. L. (1981). The classroom ration of high- and low-aptitude students and its effect on achievement. American Educational Journal, 18, 317-327.

Bernstein, B. (1960). Language and Social Class. British Journal of Sociology, 11, 271-276. Bosker, R. J. & Velden, R. van der (1989). Studieperspectieven in het onderwijs [Study perspectives in education]. In: Vogel, P., De school, keuzen en kansen: onderwijssociologische studies. Muidenberg: Coutinho.

Brown, B. W. & Saks, D. H. (1987). The microeconomics of the allocation of teachers' time and student learning. Economics of Education Review, 6, 319-332.

Brown, J. S., Collins, A. & Duguid, P. (1991). Situated knowledge and the culture of learning. Educational Researcher, 6, 319-332.

Bryk, A. S. & Raudenbush, S. W. (1992). Hierarchical linear models: Applications and data analysis methods. Newbury Park: Sage.

Coleman, J. S. & Campbell, E. Q. & Hobson, C. J. (1968). Equality of education opportunity. Washington, US Department of Health, Education and Welfare.

Crane, J. (1996). Effects of Home Environment, SES, and Maternal Test Scores on Mathematics Achievement. The Journal of Educational Research, 89, 305-314.

Creemers, B.PM. (1990). School effectiveness and effective instruction: The need for a further relationship. Paper presented at the Third International Congress on School Effectiveness and School Improvement, Jerusalem.

Dar, Y. & Resh, N. (1986). Classroom intellectual composition and academic achievement. American Educational Research Journal, 23, 357-374.

Dekkers, H.P.J.M. (1990). Seksespecifieke studiekeuzen in bet wetenschappelijk onderwijs [Gender specific choices in university education]. Nijmegen: ITS.

Duchy, FJ.R.C. (1988). The "Prior Knowledge State" of students and its facilitating effect on learning: Theories and research. OTIC report, Open Universiteit.

Edmonds, R. R. (1979). Effective schools far the urban poor. Educational Leadership, 37, 15-24. Engelhard Jr. G., Gordon, B. & Gabrielson, S. (1994). Writing tasks and gender: Influences on writing quality of black and white students. Journal of Educational Research, 87, 197-209.

Gerber, M. M. & Semmel, M. I. (1985). The microeconomics of referral and reintegration: A paradigm for evaluation of special education. Studies in Educational Evaluation, 11, 13-29. Goldstein, H, (1995). Multilevel Statistical Models, second edition. London: Edward Arnold. Hanley, E. & McKeever, M. (1997). The persistence of educational inequalities in state-socialist