The main purpose of the study was to undertake an assessment of school developmentrn'planning process in secondary schools of East Arsi zone in order to identifj, Ihe slrenglhsrnand weakness Ihen to provide allernalive recommendalions 10 Ihe idenlified prohlellls. TornIhis end. answers to the basic queslions perlaining to the performance of Ihe keyrnopera lions of planning cycle of SDP. swke holders ' involvement. illlplemenlCllion slmleg'rnand monitoring and evalualion mechanism. and potential challenges encounlered in SI)Prnprocess were sought in the study. A descriptive survey method of research was IIsed ill Ihcrnsludy. Pwposive and simple randolll sampling techniques were used in th e study. Thernsubjecls of Ihe swdy were 43 school leaders. 87 teachers. 32 studenls. 18 PTA melllbersrnalld 12 WED experts of planning and statistics frolll 6 sample woredas Ollt of 24 10101rnVoredas and 1 town administration. The data that collected through queslioll/lllire.rnilllerview and document analysis were analyzed. interpreted and reported. The collecledrndaw were analyzed using percelllage. lIIean scores. weigh led lIIean vailies IIlId chi-sqllarernlest. The fill ding of this study indicated that the extent to which the schools llelfo rllled ke'rnoperations of planning cycle slIch as school review. designing. implemelllmion andrn('mlumioll was fOlllld 10 be good. which illlplies good beginning ill Ihe praclices o/SI)Prnprocess ill secolldrllY schools of Ihe zone. However. the pareills and comlllunill'rninvolvelllent in SDP'pl'ocess and ulilizatioll 0/ data collection illSlrllm ents' wils repon edrnas low. Moreover. lack 0/ sllfficient alld conlinuolls training in the planlling process. 10lvrncommitlllellt 0/ school leaders and teachers. shorrage of materials and equiplllenls. lowrnprofessional sllpport and control. weak eXlemal cluster network. lack of collahoralivernworking and over lapping 0/ programs are the major challenges conslraining the sllccessrn0/ SDP process. Based on the major findings conclusion were drawn as ;Ihe eXlent 10rnwhich schools pelformed key operalions of planning cycle was fOllnd to be good. weakrninvolvemelll of parents and commllnily in SDP process. in sllfficient trailling in Ihernplanning process and Ihere were various problems Ihal conSlrainlS schools ill Ihe processrn0/ SDp. Therefore. il is recolllmenried Ihlll pro'idillg suslaillable Imill ing 10 iml'rol'c Iherncapacily of school leaders. teachers ami parell/s. improving Ihe involvemelll of p"relllSrnalld conllllllllily. lIIotivaling alld ellcoumgillg Ihe teachers ami leaders so liS 10 illlprOl'ernIheir r01ll 1lli11llC1I1 alld rCl'ortillg Ihe performollce of fhe school 10 parell/s. COlIl/lll1l1i/l' IIlltlrncUllcerncc/ o.Uic('s ill order /0 illlprO'C rheir sellse o/he/ollg illgness and SlIl)l'or/ u.{.'}'c/iou/.